作者 Fenix@NonceGeekDAO

0x00 目标

实现一个去中心化的Staking dApp。

本文实例亦对应 SpeedrunEthereum（一个 Ethereum 官方的开发者挑战项目）中的Challenge 0x01：

https://speedrunethereum.com/challenge/decentralized-staking

其中一个完成的例子可见：

合约：https://rinkeby.etherscan.io/address/0x4707468C95558E9B2F339c2A41DAEF483Ce11104 dApp：https://duckgo_staking.surge.sh/

0x01 What is Staking

Staking 可译为质押、质押挖矿或权益质押，是产生新区块的运算方式，由权益证明(Proof of Stake) 引伸出来。

如果您清楚比特币的运作方式，可能就会熟悉工作量证明 (PoW)。可通过该机制将交易收集到区块中。然后，这些区块会链接在一起，来创建区块链。

具体来说，矿工们会争相解出复杂的数学难题，谁先解出难题，谁就有权将下一个区块添加到区块链。事实证明，工作量证明是一种非常强大的机制，可以去中心化的方式促进达成共识。问题在于，这种机制涉及到大量的任意计算。矿工们争相解出的难题只是为了维护网络安全，别无其他目的。

然后再来看权益证明，主要理念是参与者可以锁定代币（他们的“质押权益”），在特定时间间隔内，协议会随机分配权利给其中一个人，以供验证下一个区块。通常，被选中的概率与代币数量成正比：锁定的代币越多，机会就越大。

在加密货币市场中，近年以挖矿(mining) 赚取收入的方式逐渐被质押挖矿(staking) 取代，好处是比前者减低耗电，同时又可赚取被动收入。

0x02 Speed Run Web3

可能有些同学没有接触过web3相关的开发，这里代领大家做一个speed run，方便快速入门以太坊上相关的开发。

前置

• metamask钱包

开发环境

• nodejs
• yarn
• git
• vscode

技术栈

• 框架：scaffold-eth
• 前端：react
• 合约开发：hardhat

第一步：脚手架

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

git clone https://github.com/scaffold-eth/scaffold-eth.git
cd scaffold-eth
yarn install

第二步：启动一个本地网络

cd scaffold-eth
yarn chain

第三步：部署智能合约

cd scaffold-eth
yarn deploy

第四步：打开前端页面

cd scaffold-eth
yarn start

• 技术栈
  • 顶层技术栈
  • solidity合约编程语言
  • hardhat本地开发测试链
  • react前端
  • etherseth的api sdk
  • antd前端组件ui
  • 库&组件&服务
  • Eth-components
  • Eth-services
  • 命令行
  • 底层基础
  • the graph
  • tenderly
  • etherscan
  • rpc
  • blocknative
  • L2/Sidechain Services
    • Arbitrum
    • Optimism
    • Graph Node
  • 例子
  • 通用
    • simple dao
    • Diamond Standard
    • Meta-Multi-Sig Wallet
    • Minimal Proxy
    • Minimum Viable Payment Channel
    • PunkWallet.io
    • Push The Button - Multi-player Turn Based Game
    • radwallet.io
    • Signator.io
    • Simple Stream
    • Token Allocator
    • Streaming Meta Multi Sig
  • DeFi
    • Bonding Curve
    • rTokens
    • Quadratic Funding
    • Uniswapper
    • Lender
    • Aave Flash Loans Intro
    • Aave Ape
    • DeFi Subgraphs
  • NFT
    • Simple NFT
    • Simple ERC-1155 NFT
    • Chainlink VRF NFT
    • Merkle Mint NFT
    • Nifty Viewer
    • NFT Auction
    • NFT Signature Based Auction
  • 安全
    • Honeypot
    • Re-entrancy Attack
    • Denial of Service
  • 基础设施
    • ChainLink
  • Layer2 扩展
    • Optimism Starter Pack
    • Optimism NFT
    • xNFT.io

0x03 Staking合约

我们都知道，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：

1. stake()
2. execute()
3. 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

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：

yarn chain

yarn start

yarn deploy --reset

0x04 Live Coding

4.1 stake

• 关键点1，每次质押一定数量的eth。

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

// 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

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

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

ExampleExternalContract public exampleExternalContract;

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

• 关键点3，部署的时候要初始化

// 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

uint256 public constant threshold = 1 ether;

• 关键点5，向第二个合约转账。

    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

// 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

yarn deploy --reset

• 空投测试币
• stake 一些币到达上限
• 测试 execute

4.3 withdraw

将质押的钱提取出来，这个比较简单，就是将钱转移出来即可。

    function withdraw() public {
        uint256 userBalance = balances[msg.sender];

        require(userBalance > 0, "You don't have balance to withdraw");

        balances[msg.sender] = 0;

        (bool sent, ) = msg.sender.call{value: userBalance}("");
        require(sent, "Failed to send user balance back to the user");
    }

• 完整代码如下

// 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;

    uint256 public deadline = block.timestamp + 30 seconds;

    event Stake(address indexed sender, 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");
    }

    function withdraw() public {
        uint256 userBalance = balances[msg.sender];

        require(userBalance > 0, "You don't have balance to withdraw");

        balances[msg.sender] = 0;

        (bool sent, ) = msg.sender.call{value: userBalance}("");
        require(sent, "Failed to send user balance back to the user");
    }
}

• 部署

yarn deploy --reset

• 空投测试币
• stake一些币
• 测试withdraw

4.4 加上时间或质押到期限制

这里有两个判断的标准

首先是是否到达时间，另一个就是质押是否已经完成。

• 第一个是否完成，直接去看另一个合约的标志即可

        modifier stakeNotCompleted() {
        bool completed = exampleExternalContract.completed();
        require(!completed, "staking process is already completed");
        _;
    }

• 第二个是否到时间了

  • 首先要有一个deadline变量

  uint256 public deadline = block.timestamp + 60 seconds;

  • 然后还要有一个timeLeft函数

      function timeLeft() public view returns (uint256 timeleft) {
        if (block.timestamp >= deadline) {
            return 0;
        } else {
            return deadline - block.timestamp;
        }
    }

  • 接着是deadlineReached函数

      modifier deadlineReached(bool requireReached) {
        uint256 timeRemaining = timeLeft();
        if (requireReached) {
            require(timeRemaining == 0, "deadline is not reached yet");
        } else {
            require(timeRemaining > 0, "deadline has already reached");
        }
        _;
    }

• 如何修饰这些函数

  • stake

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

  • execute函数

  function execute() public stakeNotCompleted deadlineReached(false) {
        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");
    }

  • withdraw函数

  function withdraw() public deadlineReached(true) stakeNotCompleted {
        uint256 userBalance = balances[msg.sender];
  
        require(userBalance > 0, "You don't have balance to withdraw");
  
        balances[msg.sender] = 0;
  
        (bool sent, ) = msg.sender.call{value: userBalance}("");
        require(sent, "Failed to send user balance back to the user");
    }

• 可以被外部合约调用的函数

    receive() external payable {
        stake();
    }

最终代码如下：

// 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);

    uint256 public deadline = block.timestamp + 60 seconds;

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

    modifier stakeNotCompleted() {
        bool completed = exampleExternalContract.completed();
        require(!completed, "staking process is already completed");
        _;
    }

    modifier deadlineReached(bool requireReached) {
        uint256 timeRemaining = timeLeft();
        if (requireReached) {
            require(timeRemaining == 0, "deadline is not reached yet");
        } else {
            require(timeRemaining > 0, "deadline has already reached");
        }
        _;
    }

    function timeLeft() public view returns (uint256 timeleft) {
        if (block.timestamp >= deadline) {
            return 0;
        } else {
            return deadline - block.timestamp;
        }
    }

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

    function execute() public stakeNotCompleted deadlineReached(false) {
        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");
    }

    function withdraw() public deadlineReached(true) stakeNotCompleted {
        uint256 userBalance = balances[msg.sender];

        require(userBalance > 0, "You don't have balance to withdraw");

        balances[msg.sender] = 0;

        (bool sent, ) = msg.sender.call{value: userBalance}("");
        require(sent, "Failed to send user balance back to the user");
    }

    receive() external payable {
        stake();
    }
}

• 部署

yarn deploy --reset

• 测试

0x05 相关资料

• scaffold-eth
• Web3-dApp-Camp
• https://guoyu.mirror.xyz/RD-xkpoxasAU7x5MIJmiCX4gll3Cs0pAd5iM258S1Ek
• 登链社区