Get Started with web3 Development Easily Based on Ethereum Using FMZ (2)


Get Started with web3 Development Easily Based on Ethereum Using FMZ (2)
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3/29/2024


Send ETH

In the previous course chapters, we have learned how to configure private keys. How do we know the wallet address corresponding to this private key for the configured exchange object? On FMZ, you can use the ```exchange.IO("address")``` function to obtain the wallet address corresponding to the configured private key.

The following content in this chapter uses Goerli testnet environment, so the node I am using is: ```https://goerli.infura.io/v3/*******```, and Infura assigns different node addresses for each registered user. Here the ```*******``` hides specific content.

```javascript
function main() {
let walletAddress = exchange.IO("address")
Log("Testnet goerli wallet address:", walletAddress)
}
```

After knowing your wallet address, you can use Ethereum's RPC method ```eth_getTransactionCount``` to query the transaction count of the wallet address. In Ethereum, this count is very common, and it's actually the ```nonce``` parameter that needs to be passed in during transfer operations. In Ethereum, nonce is a unique number used to ensure that each transaction is unique. It is an increasing number, and it will automatically increase every time a new transaction is sent. Therefore, when you send a transaction to a smart contract, you need to provide a nonce to ensure that the transaction is unique and in the correct order. We can find this information in some materials and documents:

> https://goethereumbook.org/en/
https://stocksharp.com/file/149802

Here, the ```PendingNonceAt``` function in the Ethereum library of Go language is actually calling the ```eth_getTransactionCount``` method. In previous courses, we have also learned how to call RPC methods. Here we use the ```exchange.IO("api", "eth", ...)``` function again.

```javascript
function toAmount(s, decimals) {
return Number((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

function main() {
let walletAddress = exchange.IO("address")
Log("Testnet goerli wallet address:", walletAddress)

/**
* eth_getTransactionCount
* @param address - string - The address from which the transaction count to be checked.
* @param blockNumber - string - The block number as a string in hexadecimal format or tags.
* @returns The integer of the number of transactions sent from an address encoded as hexadecimal.
*/
let nonce: string = exchange.IO("api", "eth", "eth_getTransactionCount", walletAddress, "pending")
Log("wallet address:", walletAddress, "current nonce:", nonce, ", convert to decimal:", toAmount(nonce, 0))
}
```

Before explaining the transfer operation, let's briefly understand some concepts. When transferring on Ethereum, a certain amount of ETH tokens will be consumed (as gas fees). The gas fee is determined by two parameters:

- gasPrice

However, the gas fees on the Ethereum network always fluctuate according to market demand and the fees users are willing to pay, so writing a fixed gas fee in the code is sometimes not an ideal choice. We can use the ```eth_gasPrice``` method we learned before, which can obtain the average gas price.

- gasLimit

A standard Ether transfer has a gas limit of 21,000 units.

After understanding the concepts of ```nonce```, ```gasPrice```, and ```gasLimit```, you can test the transfer. FMZ provides a very simple and easy-to-use transfer function.

```javascript
exchange.IO("api", "eth", "send", toAddress, toAmount)
```

When it's used for transfers, the third parameter of ```exchange.IO``` is fixed as "send", the ```toAddress``` parameter is the address receiving ETH during the transfer, and ```toAmount``` is the amount of ETH transferred.

The parameters ```nonce```, ```gasPrice```, and ```gasLimit``` can all use system default values automatically obtained on FMZ. They can also be specified:

```javascript
exchange.IO("api", "eth", "send", toAddress, toAmount, {gasPrice: 5000000000, gasLimit: 21000, nonce: 100})
```

Next, we will transfer a certain amount of ETH to a specific address on the goerli test network:

```javascript
function toInnerAmount(s, decimals) {
return (BigDecimal(s)*BigDecimal(Math.pow(10, decimals))).toFixed(0)
}

function main() {
let walletAddress = exchange.IO("address")
Log("Testnet goerli wallet address:", walletAddress)

let ret = exchange.IO("api", "eth", "send", "0x4D75a08E870674E68cAE611f329A27f446A66813", toInnerAmount(0.01, 18))
return ret // return Transaction Hash : 0xa6f9f51b00d8ae850b0f204380b59da98f4bbce34b813577d3d948f61de4734e
}
```

Because the unit of Ethereum transfer amount is ```wei```, a custom function ```toInnerAmount``` needs to be used to process the value in ```wei``` units.

Query Transaction Hash: ```0xa6f9f51b00d8ae850b0f204380b59da98f4bbce34b813577d3d948f61de4734e``` on ```https://etherscan.io/```.
https://stocksharp.com/file/149803

You can also write code to query transfer hash ```0xa6f9f51b00d8ae850b0f204380b59da98f4bbce34b813577d3d948f61de4734e```, using the ```eth_getTransactionReceipt``` method for queries.

```javascript
function main() {
let transHash = "0xa6f9f51b00d8ae850b0f204380b59da98f4bbce34b813577d3d948f61de4734e"
let info = exchange.IO("api", "eth", "eth_getTransactionReceipt", transHash)
return info
}
```

Query result:

```run
{
"cumulativeGasUsed": "0x200850",
"effectiveGasPrice": "0x1748774421",
"transactionHash": "0xa6f9f51b00d8ae850b0f204380b59da98f4bbce34b813577d3d948f61de4734e",
"type": "0x0",
"blockHash": "0x6bdde8b0f0453ecd24eecf7c634d65306f05511e0e8f09f9ed3f59eee2d06ac7",
"contractAddress": null,
"blockNumber": "0x868a50",
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
"gasUsed": "0x5208",
"to": "0x4d75a08e870674e68cae611f329a27f446a66813",
"status": "0x1",
"transactionIndex": "0x23",
"from": "0x6b3f11d807809b0b1e5e3243df04a280d9f94bf4",
"logs": []
}
```

Description corresponding to each field:

```desc
blockHash - The hash value of the block where the transaction is located.
blockNumber - The block number of the block where the transaction is located, encoded in hexadecimal.
contractAddress - If it's a contract creation, the address of the contract; otherwise null.
cumulativeGasUsed - The total gas used when executing this transaction in the block.
effectiveGasPrice - Total base fee plus tip per unit of gas.
from - Sender's address.
gasUsed - Gas used by this specific transaction.
logs - Array of log objects generated by this transaction.
address - Address that generated this log.
topics - Data array with 0 to 4 indexed log parameters, each with 32 bytes. In Solidity, first topic is event signature hash (e.g., Deposit(address,bytes32,uint256)), unless you declare an event using anonymous specifier.
data - Non-indexed parameters for logs with length of 32 bytes.
blockNumber - The block number of the block where this log is located.
transactionHash - Transaction hash at time when log was created. Null if pending state.
transactionIndex - Index position during creation. Null if pending state.
blockHash - The hash value for containing block.
logIndex - Hexadecimal-encoded integer index position within containing block. Null if pending state.
removed - True if deleted due to chain reorganization; false for valid logs.
logsBloom - Bloom filter for retrieving related logs.
status - Hexadecimal-encoded value either being '1' (success) or '0' (failure).
to - Receiving party's address; null for contract creation transactions.
transactionHash - The hash value associated with given transaction.
transactionIndex - Hexadecimal-encoded index position within its respective containing-block.
type - Type value.
```



Call Ethereum Smart Contract
In the chapter on "Reading Contract Information", we used a complete example to call the method of ENS contract deployed on Ethereum to obtain Vitalik Buterin's wallet address. These methods belong to ```Read``` methods, and calling these methods does not require ```gas``` (remember what we talked about gas before?). In this chapter, we will call some ```Write``` methods of smart contracts on Ethereum and pay for ```gas```. These operations will be verified by each node and miner in the entire network and change the blockchain state.

ERC20

For the ERC20 contract (ERC20 token contract), FMZ platform lists the ABI of the ERC20 contract ABI as a common ABI built directly into the system, eliminating the step of registering the ABI. We have also learned about ABI in previous tutorials when we registered ENS contract's ABI before calling ENS contract methods.

To better understand ABI, you can check it out before using it. Here is the ABI for ERC20 contracts:

```javascript
[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"guy","type":"address"},{"name":"wad","type":"uint256"}],"name":"approve","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"src","type":"address"},{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"wad","type":"uint256"}],"name":"withdraw","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"deposit","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"},{"name":"","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"guy","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Deposit","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Withdrawal","type":"event"}]
```

This section uses the ```Goerli``` testnet environment.

balanceOf

Next, let's practice again how to call the ```Read``` method of a contract to read contract information, call the ```balanceOf``` method of ERC20 contract to query token balance, the balanceOf method has only one parameter, which is not named, but can be identified by its type as an address (i.e., the address of the token being queried). Since the returned data is not in units of one token, we also need the precision data of tokens for conversion. The precision of tokens can be obtained by using ```decimals``` method in ERC20 contracts. We will use Ethereum testnet ```goerli``` for testing. Please note that token contract addresses may vary on different chains.

```javascript
function toAmount(s, decimals) {
return Number((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

function main() {
let walletAddress = exchange.IO("address")

// goerli WETH address
let wethAddress = "0xB4FBF271143F4FBf7B91A5ded31805e42b2208d6"
// goerli LINK address
let linkAddress = "0x326C977E6efc84E512bB9C30f76E30c160eD06FB"

// Since it is an ERC20 contract, FMZ has built-in ABI registration, so there is no need to register ERC20 ABI here.
let wethDecimals = exchange.IO("api", wethAddress, "decimals")
let linkDecimals = exchange.IO("api", linkAddress, "decimals")

let wethBalance = exchange.IO("api", wethAddress, "balanceOf", walletAddress)
let linkBalance = exchange.IO("api", linkAddress, "balanceOf", walletAddress)
Log("WETH precision:", wethDecimals, "wethBalance:", toAmount(wethBalance, wethDecimals))
Log("LINK precision:", linkDecimals, "linkBalance:", toAmount(linkBalance, linkDecimals))
}
```

By running the above code, you can query the current wallet's WETH and LINK token balance:

> WETH precision: 18 wethBalance: 0
> LINK precision: 18 linkBalance: 51.41374973681053

deposit
We can see that the balance of WETH tokens in the wallet is 0. Next, we will continue to interact with the ERC20 smart contract of WETH tokens, and this time we will call the Write type method: ```deposit```.
The function of the ```deposit``` method is simply to exchange a certain amount of ETH for WETH. It should be noted that there are no parameters for the ```deposit``` method (which can be observed by checking ABI). The ```payable``` attribute of this method is ```true```, so when calling it, you need to set the transferable ETH (payableAmount) quantity to specify the amount of ETH deposited.

> Pay attention when calling smart contract methods:
> If the called method has a payable attribute, you need to add a transfer ETH value (the fourth parameter of the exchange.IO function) after the method name, which can be a numeric type or a string form of numeric value.

```javascript
function toAmount(s, decimals) {
return Number((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

function toInnerAmount(s, decimals) {
return (BigDecimal(s)*BigDecimal(Math.pow(10, decimals))).toFixed(0)
}

function main() {
let walletAddress = exchange.IO("address")

// goerli WETH address
let wethAddress = "0xB4FBF271143F4FBf7B91A5ded31805e42b2208d6"

// Since it is an ERC20 contract, FMZ has built-in ABI registration, so there is no need to register ERC20 ABI here.
let wethDecimals = exchange.IO("api", wethAddress, "decimals")

let wethBalance = exchange.IO("api", wethAddress, "balanceOf", walletAddress)
Log("WETH precision:", wethDecimals, "wethBalance:", toAmount(wethBalance, wethDecimals))
let ethBalance = exchange.IO("api", "eth", "eth_getBalance", walletAddress, "latest")
Log("ETH precision:", 18, "ethBalance:", toAmount(ethBalance, 18))

// Call the deposit method, since deposit is a method outside of the ERC20 standard, we need to register the ABI for this method here
let abiWETH = `[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"guy","type":"address"},{"name":"wad","type":"uint256"}],"name":"approve","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"src","type":"address"},{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"wad","type":"uint256"}],"name":"withdraw","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"deposit","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"},{"name":"","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"guy","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Deposit","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Withdrawal","type":"event"}]`
exchange.IO("abi", wethAddress, abiWETH)

let payableAmount = toInnerAmount(0.01, 18)
let ret = exchange.IO("api", wethAddress, "deposit", payableAmount)
Log("Transaction Hash:", ret)
}
```

> WETH precision: 18 wethBalance: 0
> ETH precision: 18 ethBalance: 0.14333094664072302
> Transaction Hash: 0xaf15b0b0e25a81eda583295e82b249e2d02e4eafebecc906470ccc2c89e23563
https://stocksharp.com/file/149804

Check the balance of WETH and ETH again:

> WETH precision: 18 wethBalance: 0.01
> ETH precision: 18 ethBalance: 0.1333309358060905

Before calling ```deposit```, ```WETH``` is 0 and ```ETH``` is 0.14333094664072302. After calling ```deposit```, ```WETH``` is 0.01 and ```ETH``` is 0.1333309358060905. It can be seen that it has exchanged 0.01```ETH``` for ```WETH``` successfully.

transfer
ERC20 tokens can also be transferred, using the ```transfer``` method to transfer 0.01 WETH tokens to the address ```0x4D75a08E870674E68cAE611f329A27f446A66813```. The ```transfer``` method has two parameters, the first parameter ```dst``` is the wallet address of the transfer recipient, and the second parameter ```wad``` is the transfer amount.

```javascript
function toAmount(s, decimals) {
return Number((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

function toInnerAmount(s, decimals) {
return (BigDecimal(s)*BigDecimal(Math.pow(10, decimals))).toFixed(0)
}

function waitMined (tx) {
for (var i = 0 ; i < 10 ; i++) {
Sleep(5000)
let info = exchange.IO("api", "eth", "eth_getTransactionReceipt", tx)
if (info && info.gasUsed) {
Log(info)
return true
}
Log('Transaction not yet mined', tx)
}
return false
}

function main() {
let walletAddress = exchange.IO("address")

// goerli WETH address
let wethAddress = "0xB4FBF271143F4FBf7B91A5ded31805e42b2208d6"

// Since it is an ERC20 contract, FMZ has built-in ABI registration, there is no need to register ERC20 ABI here.
let wethDecimals = exchange.IO("api", wethAddress, "decimals")
let wethBalance = exchange.IO("api", wethAddress, "balanceOf", walletAddress)
Log("WETH precision:", wethDecimals, "wethBalance:", toAmount(wethBalance, wethDecimals))

let dst = "0x4D75a08E870674E68cAE611f329A27f446A66813"
let wad = toInnerAmount(0.01, wethDecimals)
let tx = exchange.IO("api", wethAddress, "transfer", dst, wad)
Log("Transaction Hash:", tx)
waitMined(tx)

wethBalance = exchange.IO("api", wethAddress, "balanceOf", walletAddress)
Log("WETH precision:", wethDecimals, "wethBalance:", toAmount(wethBalance, wethDecimals))
}
```

In the above example, a custom function ```waitMined``` is used. In fact, we are not unfamiliar with the function of this function. Do you remember the ```eth_getTransactionReceipt``` method? The purpose of this waitMined custom function is to wait for the result of the passed Transaction Hash.

For this WETH transfer, interested readers can also query the Transaction Hash ```0x2fafb62b548a1fffb0f3189429e3c5a4f57ddafb0acbc0678d8b3cf0a2f7c92c``` to view details (note that it is on testnet goerli).

withdraw

This time we will exchange ```WETH``` back to ```ETH```, using the ```withdraw``` method, which has only one parameter ```wad```, simply put, it is used to set how much ETH to exchange back.

```javascript
function toAmount(s, decimals) {
return Number((BigDecimal(BigInt(s)) / BigDecimal(Math.pow(10, decimals))).toString())
}

function toInnerAmount(s, decimals) {
return (BigDecimal(s)*BigDecimal(Math.pow(10, decimals))).toFixed(0)
}

function main() {
let walletAddress = exchange.IO("address")

// goerli WETH address
let wethAddress = "0xB4FBF271143F4FBf7B91A5ded31805e42b2208d6"

// Since it is an ERC20 contract, FMZ has built-in ABI registration, there is no need to register ERC20 ABI here.
let wethDecimals = exchange.IO("api", wethAddress, "decimals")

let wethBalance = exchange.IO("api", wethAddress, "balanceOf", walletAddress)
Log("WETH precision:", wethDecimals, "wethBalance:", toAmount(wethBalance, wethDecimals))
let ethBalance = exchange.IO("api", "eth", "eth_getBalance", walletAddress, "latest")
Log("ETH precision:", 18, "ethBalance:", toAmount(ethBalance, 18))

let abiWETH = `[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"guy","type":"address"},{"name":"wad","type":"uint256"}],"name":"approve","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"src","type":"address"},{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"wad","type":"uint256"}],"name":"withdraw","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"name":"","type":"bool"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[],"name":"deposit","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"},{"name":"","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"guy","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"dst","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Deposit","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"src","type":"address"},{"indexed":false,"name":"wad","type":"uint256"}],"name":"Withdrawal","type":"event"}]`
exchange.IO("abi", wethAddress, abiWETH)

let wad = toInnerAmount(0.01, 18)
let ret = exchange.IO("api", wethAddress, "withdraw", wad)
Log("Transaction Hash:", ret)
}
```

> Transaction Hash: 0x446423c841451a8d04428a075b556eb5564186b09926da915f5da1c9837d2af4

From the above code, it can be seen that it is basically the same as the previous example, except that the method called in the last step is changed to ```withdraw```, before calling:

> WETH precision: 18 wethBalance: 0.01
> ETH precision: 18 ethBalance: 0.11322979983231546

Query again:

> WETH precision: 18 wethBalance: 0
> ETH precision: 18 ethBalance: 0.1231207156449464

We can see that 0.01 ```WETH``` has been exchanged back to ```ETH```.

Uniswap V3

```Uniswap V3``` is a decentralized transaction protocol built on the Ethereum blockchain, used to facilitate cryptocurrency trading and liquidity provision. It consists of a series of smart contracts, including core contracts, pool contracts, factory contracts, router contracts, etc.

The following contracts are mainly used when querying the current exchange price and performing exchange operations using ```Uniswap```:

- ```Router``` (Router contract)
This is the contract used to execute transactions, allowing the user to perform a trade operation by specifying a trade path and parameters.
- ```Pool``` (Pool contract)
Pool contracts are the key component in ```Uniswap``` for storing and managing the liquidity of a given asset pair. Each asset pair has a corresponding pool contract, which contains information about the funds, price range, fee settings, etc. provided by the liquidity provider. The pool contract is responsible for processing transactions, calculating the status of the pool, and ensuring the smooth execution of transactions.
- ```Factory``` (Factory contract)
Factory contracts are the contracts used to create and manage ```Uniswap``` pool contracts. When users wish to create new asset pairs, they deploy new pool contracts by interacting with the factory contract. Factory contracts are responsible for coordinating the creation and initialization of pool contracts, enabling users to create new asset pairs dynamically.

As we have learned in previous lessons, let's review how to register the ```ABI``` of smart contracts in strategy code on the FMZ Quant Trading Platform. The process of obtaining the ABI of smart contracts has been discussed in previous lessons and will not be repeated here.
Three ```Uniswap``` smart contract ```ABI```s need to be registered, using the Ethereum mainnet as an example:

```javascript
var abiRoute = 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var abiPool = 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\"amount\",\"type\":\"uint128\"}],\"name\":\"burn\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amount0\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amount1\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"recipient\",\"type\":\"address\"},{\"internalType\":\"int24\",\"name\":\"tickLower\",\"type\":\"int24\"},{\"internalType\":\"int24\",\"name\":\"tickUpper\",\"type\":\"int24\"},{\"internalType\":\"uint128\",\"name\":\"amount0Requested\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"amount1Requested\",\"type\":\"uint128\"}],\"name\":\"collect\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"amount0\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"amount1\",\"type\":\"uint128\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"recipient\",\"type\":\"address\"},{\"internalType\":\"uint128\",\"name\":\"amount0Requested\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"amount1Requested\",\"type\":\"uint128\"}],\"name\":\"collectProtocol\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"amount0\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"amount1\",\"type\":\"uint128\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"factory\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"fee\",\"outputs\":[{\"internalType\":\"uint24\",\"name\":\"\",\"type\":\"uint24\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"feeGrowthGlobal0X128\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"feeGrowthGlobal1X128\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"recipient\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"amount0\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amount1\",\"type\":\"uint256\"},{\"internalType\":\"bytes\",\"name\":\"data\",\"type\":\"bytes\"}],\"name\":\"flash\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint16\",\"name\":\"observationCardinalityNext\",\"type\":\"uint16\"}],\"name\":\"increaseObservationCardinalityNext\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint160\",\"name\":\"sqrtPriceX96\",\"type\":\"uint160\"}],\"name\":\"initialize\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"liquidity\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"\",\"type\":\"uint128\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"maxLiquidityPerTick\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"\",\"type\":\"uint128\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"recipient\",\"type\":\"address\"},{\"internalType\":\"int24\",\"name\":\"tickLower\",\"type\":\"int24\"},{\"internalType\":\"int24\",\"name\":\"tickUpper\",\"type\":\"int24\"},{\"internalType\":\"uint128\",\"name\":\"amount\",\"type\":\"uint128\"},{\"internalType\":\"bytes\",\"name\":\"data\",\"type\":\"bytes\"}],\"name\":\"mint\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amount0\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amount1\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"name\":\"observations\",\"outputs\":[{\"internalType\":\"uint32\",\"name\":\"blockTimestamp\",\"type\":\"uint32\"},{\"internalType\":\"int56\",\"name\":\"tickCumulative\",\"type\":\"int56\"},{\"internalType\":\"uint160\",\"name\":\"secondsPerLiquidityCumulativeX128\",\"type\":\"uint160\"},{\"internalType\":\"bool\",\"name\":\"initialized\",\"type\":\"bool\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint32[]\",\"name\":\"secondsAgos\",\"type\":\"uint32[]\"}],\"name\":\"observe\",\"outputs\":[{\"internalType\":\"int56[]\",\"name\":\"tickCumulatives\",\"type\":\"int56[]\"},{\"internalType\":\"uint160[]\",\"name\":\"secondsPerLiquidityCumulativeX128s\",\"type\":\"uint160[]\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"bytes32\",\"name\":\"\",\"type\":\"bytes32\"}],\"name\":\"positions\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"liquidity\",\"type\":\"uint128\"},{\"internalType\":\"uint256\",\"name\":\"feeGrowthInside0LastX128\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"feeGrowthInside1LastX128\",\"type\":\"uint256\"},{\"internalType\":\"uint128\",\"name\":\"tokensOwed0\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"tokensOwed1\",\"type\":\"uint128\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"protocolFees\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"token0\",\"type\":\"uint128\"},{\"internalType\":\"uint128\",\"name\":\"token1\",\"type\":\"uint128\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint8\",\"name\":\"feeProtocol0\",\"type\":\"uint8\"},{\"internalType\":\"uint8\",\"name\":\"feeProtocol1\",\"type\":\"uint8\"}],\"name\":\"setFeeProtocol\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"slot0\",\"outputs\":[{\"internalType\":\"uint160\",\"name\":\"sqrtPriceX96\",\"type\":\"uint160\"},{\"internalType\":\"int24\",\"name\":\"tick\",\"type\":\"int24\"},{\"internalType\":\"uint16\",\"name\":\"observationIndex\",\"type\":\"uint16\"},{\"internalType\":\"uint16\",\"name\":\"observationCardinality\",\"type\":\"uint16\"},{\"internalType\":\"uint16\",\"name\":\"observationCardinalityNext\",\"type\":\"uint16\"},{\"internalType\":\"uint8\",\"name\":\"feeProtocol\",\"type\":\"uint8\"},{\"internalType\":\"bool\",\"name\":\"unlocked\",\"type\":\"bool\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"int24\",\"name\":\"tickLower\",\"type\":\"int24\"},{\"internalType\":\"int24\",\"name\":\"tickUpper\",\"type\":\"int24\"}],\"name\":\"snapshotCumulativesInside\",\"outputs\":[{\"internalType\":\"int56\",\"name\":\"tickCumulativeInside\",\"type\":\"int56\"},{\"internalType\":\"uint160\",\"name\":\"secondsPerLiquidityInsideX128\",\"type\":\"uint160\"},{\"internalType\":\"uint32\",\"name\":\"secondsInside\",\"type\":\"uint32\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"recipient\",\"type\":\"address\"},{\"internalType\":\"bool\",\"name\":\"zeroForOne\",\"type\":\"bool\"},{\"internalType\":\"int256\",\"name\":\"amountSpecified\",\"type\":\"int256\"},{\"internalType\":\"uint160\",\"name\":\"sqrtPriceLimitX96\",\"type\":\"uint160\"},{\"internalType\":\"bytes\",\"name\":\"data\",\"type\":\"bytes\"}],\"name\":\"swap\",\"outputs\":[{\"internalType\":\"int256\",\"name\":\"amount0\",\"type\":\"int256\"},{\"internalType\":\"int256\",\"name\":\"amount1\",\"type\":\"int256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"int16\",\"name\":\"\",\"type\":\"int16\"}],\"name\":\"tickBitmap\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"tickSpacing\",\"outputs\":[{\"internalType\":\"int24\",\"name\":\"\",\"type\":\"int24\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"int24\",\"name\":\"\",\"type\":\"int24\"}],\"name\":\"ticks\",\"outputs\":[{\"internalType\":\"uint128\",\"name\":\"liquidityGross\",\"type\":\"uint128\"},{\"internalType\":\"int128\",\"name\":\"liquidityNet\",\"type\":\"int128\"},{\"internalType\":\"uint256\",\"name\":\"feeGrowthOutside0X128\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"feeGrowthOutside1X128\",\"type\":\"uint256\"},{\"internalType\":\"int56\",\"name\":\"tickCumulativeOutside\",\"type\":\"int56\"},{\"internalType\":\"uint160\",\"name\":\"secondsPerLiquidityOutsideX128\",\"type\":\"uint160\"},{\"internalType\":\"uint32\",\"name\":\"secondsOutside\",\"type\":\"uint32\"},{\"internalType\":\"bool\",\"name\":\"initialized\",\"type\":\"bool\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"token0\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"token1\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"}]'
var abiFactory = '[{\"inputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"constructor\"},{\"anonymous\":false,\"inputs\":[{\"indexed\":true,\"internalType\":\"uint24\",\"name\":\"fee\",\"type\":\"uint24\"},{\"indexed\":true,\"internalType\":\"int24\",\"name\":\"tickSpacing\",\"type\":\"int24\"}],\"name\":\"FeeAmountEnabled\",\"type\":\"event\"},{\"anonymous\":false,\"inputs\":[{\"indexed\":true,\"internalType\":\"address\",\"name\":\"oldOwner\",\"type\":\"address\"},{\"indexed\":true,\"internalType\":\"address\",\"name\":\"newOwner\",\"type\":\"address\"}],\"name\":\"OwnerChanged\",\"type\":\"event\"},{\"anonymous\":false,\"inputs\":[{\"indexed\":true,\"internalType\":\"address\",\"name\":\"token0\",\"type\":\"address\"},{\"indexed\":true,\"internalType\":\"address\",\"name\":\"token1\",\"type\":\"address\"},{\"indexed\":true,\"internalType\":\"uint24\",\"name\":\"fee\",\"type\":\"uint24\"},{\"indexed\":false,\"internalType\":\"int24\",\"name\":\"tickSpacing\",\"type\":\"int24\"},{\"indexed\":false,\"internalType\":\"address\",\"name\":\"pool\",\"type\":\"address\"}],\"name\":\"PoolCreated\",\"type\":\"event\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"tokenA\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"tokenB\",\"type\":\"address\"},{\"internalType\":\"uint24\",\"name\":\"fee\",\"type\":\"uint24\"}],\"name\":\"createPool\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"pool\",\"type\":\"address\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint24\",\"name\":\"fee\",\"type\":\"uint24\"},{\"internalType\":\"int24\",\"name\":\"tickSpacing\",\"type\":\"int24\"}],\"name\":\"enableFeeAmount\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint24\",\"name\":\"\",\"type\":\"uint24\"}],\"name\":\"feeAmountTickSpacing\",\"outputs\":[{\"internalType\":\"int24\",\"name\":\"\",\"type\":\"int24\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"},{\"internalType\":\"uint24\",\"name\":\"\",\"type\":\"uint24\"}],\"name\":\"getPool\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"owner\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"parameters\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"factory\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"token0\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"token1\",\"type\":\"address\"},{\"internalType\":\"uint24\",\"name\":\"fee\",\"type\":\"uint24\"},{\"internalType\":\"int24\",\"name\":\"tickSpacing\",\"type\":\"int24\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"_owner\",\"type\":\"address\"}],\"name\":\"setOwner\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"}]'

var contractV3FactoryAddress = "0x1F98431c8aD98523631AE4a59f267346ea31F984"
var contractV3SwapRouterV2Address = "0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45"

function main() {
// ABI for registration of Uniswap factory contracts
exchange.IO("abi", contractV3FactoryAddress, abiFactory)

// Test the owner method of the Factory contract
var owner = exchange.IO("api", contractV3FactoryAddress, "owner")
Log("owner:", owner) // The return value should be: 0x1a9C8182C09F50C8318d769245beA52c32BE35BC

// Register ABI for Uniswap router contracts
exchange.IO("abi", contractV3SwapRouterV2Address, abiRoute)

// Factory method for testing Uniswap V3 Router V2 contracts
var factoryOfRouter = exchange.IO("api", contractV3SwapRouterV2Address, "factory")
Log("factoryOfRouter:", factoryOfRouter) // The return value should be: 0x1F98431c8aD98523631AE4a59f267346ea31F984

// Get the pool address of the trading pair
var tokenIn = {name : "DAI", address: "0x6b175474e89094c44da98b954eedeac495271d0f"}
var tokenOut = {name : "USDT", address: "0xdac17f958d2ee523a2206206994597c13d831ec7"}
var poolAddress = exchange.IO("api", contractV3FactoryAddress, "getPool", tokenIn.address, tokenOut.address, 3000)
var pair = "tokenIn:" + tokenIn.name + ", tokenOut:" + tokenOut.name + ", fee:" + 3000
Log("Use the getPool method of the factory contract to get", pair, "pool address:", poolAddress)

// Registration pool contract ABI
exchange.IO("abi", poolAddress, abiPool)

// Test pool contract
var factoryOfPool = exchange.IO("api", poolAddress, "factory")
Log("factoryOfPool:", factoryOfPool) // The return value should be: 0x1F98431c8aD98523631AE4a59f267346ea31F984
}
```

The above code registered the ABI of the factory contract, router contract and pool contract and did some tests. It can be observed that the ```factory``` method of both the router contract and the pool contract return the address ```0x1F98431c8aD98523631AE4a59f267346ea31F984```, which is the address of the Uniswap factory contract (variable ``` contractV3FactoryAddress``` in the code).

```javascript
var contractV3FactoryAddress = "0x1F98431c8aD98523631AE4a59f267346ea31F984"
```

After registering the ABI of the smart contract, next we look at the exchange operation using ```Uniswap V3``` first, and in the following we use the exchange of ```ERC20``` tokens (on the Ethereum mainnet) as a specific scenario.

To be continued...




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