thegraph notes step by step

Installation Environment

Truffle && Ganache

Truffle is the most comprehensive smart contract development suite

• Built-in smart contract compilation, linking, deployment and binary management.

• Advanced debugging with breakpoints, variable analysis, and step functionality.

• Truffle is written based on JavaScript and can be debugged using console.log in smart contracts

• Deploy and trade with MetaMask and Truffle Dashboard, protecting your mnemonic.

• An external script runner that executes scripts within the Truffle environment.

• Automated contract testing for rapid development.

• Use NPM for package management, using the ERC190 standard

• Scriptable, scalable deployment and migration architecture

• Interactive console available for contract communication

# 安装node
nvm install 18

# 安装Truffle
npm install -g truffle
# 查看Truffle版本
truffle version

# 安卓ganache
https://trufflesuite.com/docs/ganache/quickstart/

Install IDE plugins

https://marketplace.visualstudio.com/items?itemName=trufflesuite-csi.truffle-vscode

https://trufflesuite.com/blog/build-on-web3-with-truffle-vs-code-extension/

vscodeInstall Truffle for VS Code

Instructions for use

https://blog.csdn.net/VictorXSS/article/details/127852997

In this document, pay attention to adding 2_deploy_contracts.js in migrations

In this way, the deploy can be successful

solidity code

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;

contract Pair{

    string private _name;

    uint private _liquidity;

    constructor(string memory name){
        _name = name;
    }

    function addLiquidity(uint amount) public {
        _liquidity+=amount;
    }

    function getLiquidity() public view returns(uint){
        return _liquidity;
    }

    function getName() public view returns(string memory){
        return _name;
    }

}

contract Dex {

    address private _owner;

    uint private _index = 0;

    mapping(address => Pair) private _pairs;

    mapping(uint => address) private _indexs;

    modifier onlyOwner(){
        require(msg.sender == _owner,"must be owner");
        _;
    }

    event PairCreated(string name, address pairAddress);

    event AddLiquidity(address pairAddress, uint liquidity);


    function createPair(string memory name) public {
        Pair pair = new Pair(name);
        _pairs[address(pair)] = pair;
        _indexs[_index] = address(pair);
        _index++;

        emit PairCreated(name, address(pair));
    }

    function addLiquidity(address pairedAddress,uint liquidity) public {
        _pairs[pairedAddress].addLiquidity(liquidity);

        emit AddLiquidity(pairedAddress,liquidity);
    }


    function getCount() public view returns(uint){
        return _index;
    }

    function pairAddress(uint index) public view returns(address){
        return _indexs[index];
    }

    
    function getPairName(address pairedAddress) public view returns(string memory){
        return _pairs[pairedAddress].getName();
    }


    function getLiquidity(address pairedAddress) public view returns(uint liquidity){
        return _pairs[pairedAddress].getLiquidity();
    }
}

core code

# solidity 里的代码       
emit PairCreated(name, address(pair));

emit AddLiquidity(pairAddress,liquidity);

# subgraph.yaml    

eventHandlers:
       - event: PairCreated(string,address)
         handler: handleNewPairCreated
       - event: AddLiquidity(address,uint256)
         handler: handleAddLiquidity

import {AddLiquidity, PairCreated} from '../generated/study/Dex'
import {Pair} from '../generated/schema'

export function handleNewPairCreated(event: PairCreated): void {
    let pair = new Pair(event.params.pairAddress.toHexString())
    pair.displayName = event.params.name
    pair.liquidity = 0
    pair.save()
}

export function handleAddLiquidity(event: AddLiquidity): void {
    let id = event.params.pairAddress.toHexString()
    let pair = Pair.load(id)
    if (pair == null) {
        return
    }
    pair.liquidity += event.params.liquidity.toI32()
    pair.save()
}

• PairCreated is the emit method in solidity

• handleNewPairCreated is the code in mapping.ts

• When PairCreated in solidity is called, handleNewPairCreated will be triggered to save the data. Save data can be database or file

• The trigger is provided by the provider

• provider 是Web3 provider is a website running geth or parity node which talks to Ethereum network.

参考

https://blog.csdn.net/u013705066/article/details/123573546

https://blog.quicknode.com/the-importance-of-web3-provider-redundancy

https://ethereum.stackexchange.com/questions/31218/what-are-providers-in-the-ethereum

https://techfi.tech/introduction-to-the-graph-the-google-of-web3/

https://thegraph.academy/developers/local-development/