如何开发DAPP丨LP丨IDO预售代币智能合约系统开发流程详细及源码

dApp开发最重要的就是编写智能合约，我们先来分析一下Staking合约的基本格式。

在一定时间（deadline）内，质押（stake）一定数量（threshold）的代币。到期之后可以将代币转入（execute）到另一个合约，也可以将代币提取出来（withdraw）。

所以我们抽像出来了三个关键函数：

stake()
execute()
withdraw()

scaffold-eth也为我们提供了这样的一个脚手架，只需要把代码拉下来，我们本次就在这个基础上逐步来实现。

https://github.com/scaffold-eth/scaffold-eth-challenges

代码语言：javascript复制

git clone https://github.com/scaffold-eth/scaffold-eth-challenges.git
cd scaffold-eth-challenges
git checkout challenge-1-decentralized-staking
yarn install

然后开三个终端窗口，执行如下三个命令：

代码语言：javascript复制

yarn chain

代码语言：javascript复制

yarn start

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yarn deploy --reset

0x04 Live Coding

4.1 stake

关键点1，每次质押一定数量的eth。

代码语言：javascript复制

pragma solidity 0.8.4;

import "hardhat/console.sol";
import "./ExampleExternalContract.sol";

contract Staker {
    mapping(address => uint256) public balances;

    event Stake(address indexed staker, uint256 amount);

    function stake() public payable {
        balances[msg.sender]  = msg.value;
        emit Stake(msg.sender, msg.value);
    }
}

关键点2，部署脚本移除构造函数的参数

代码语言：javascript复制

// deploy/01_deploy_staker.js
// ....

await deploy("Staker", {
    // Learn more about args here: https://www.npmjs.com/package/hardhat-deploy#deploymentsdeploy
    from: deployer,
    // args: [exampleExternalContract.address],
    log: true,
  });

//...

关键点3，部署

代码语言：javascript复制

yarn deploy --reset

关键点4，空投一些测试币
关键点5，测试stake

4.2 execute

筹集到的资金，在满足一定条件之后，转移给另一个合约中。

关键点1，另一个合约

代码语言：javascript复制

contract ExampleExternalContract {

  bool public completed;

  function complete() public payable {
    completed = true;
  }

}

很简单，有一个flag代表是否已经结束了。

关键点2，构造函数

在stake合约中，要把这个合约引入进来，同时要有一个构造函数

代码语言：javascript复制

ExampleExternalContract public exampleExternalContract;

constructor(address exampleExternalContractAddress) public {
        exampleExternalContract = ExampleExternalContract(
            exampleExternalContractAddress
        );
}

关键点3，部署的时候要初始化

代码语言：javascript复制

// deploy/01_deploy_staker.js
// ....

await deploy("Staker", {
    // Learn more about args here: https://www.npmjs.com/package/hardhat-deploy#deploymentsdeploy
    from: deployer,
    args: [exampleExternalContract.address],
    log: true,
  });

//...

关键点4，质押上限

代码语言：javascript复制

uint256 public constant threshold = 1 ether;

关键点5，向第二个合约转账。

代码语言：javascript复制

    function execute() public {
        uint256 contractBalance = address(this).balance;

        // check the contract has enough ETH to reach the treshold
        require(contractBalance >= threshold, "Threshold not reached");

        // Execute the external contract, transfer all the balance to the contract
        // (bool sent, bytes memory data) = exampleExternalContract.complete{value: contractBalance}();
        (bool sent, ) = address(exampleExternalContract).call{
            value: contractBalance
        }(abi.encodeWithSignature("complete()"));
        require(sent, "exampleExternalContract.complete failed");
    }

最终代码如下

代码语言：javascript复制

// SPDX-License-Identifier: MIT
pragma solidity 0.8.4;

import "hardhat/console.sol";
import "./ExampleExternalContract.sol";

contract Staker {
    ExampleExternalContract public exampleExternalContract;

    mapping(address => uint256) public balances;
    
    uint256 public constant threshold = 1 ether;

    event Stake(address indexed staker, uint256 amount);

    constructor(address exampleExternalContractAddress) public {
        exampleExternalContract = ExampleExternalContract(
            exampleExternalContractAddress
        );
    }

    function stake() public payable {
        balances[msg.sender]  = msg.value;
        emit Stake(msg.sender, msg.value);
    }

    function execute() public {
        uint256 contractBalance = address(this).balance;

        require(contractBalance >= threshold, "Threshold not reached");

        (bool sent, ) = address(exampleExternalContract).call{
            value: contractBalance
        }(abi.encodeWithSignature("complete()"));
        require(sent, "exampleExternalContract.complete() failed");
    }
}

部署

代码语言：javascript复制

yarn deploy --reset

空投测试币
stake 一些币到达上限
测试 execute

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