truffle框架创建合约实例代码

本文介绍如何使用Truffle框架在React应用中部署并调用智能合约。通过实例演示了从获取Web3实例到设置合约提供者,再到调用合约方法的全过程。

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truffle框架来创建合约实例的代码如下:

import React, { Component } from "react";
import SimpleStorageContract from "./contracts/SimpleStorage.json";
import getWeb3 from "./utils/getWeb3";
import truffleContract from "truffle-contract";

import "./App.css";

class App extends Component {
  state = { storageValue: 0, web3: null, accounts: null, contract: null };

  componentDidMount = async () => {
    try {
      // Get network provider and web3 instance.
      const web3 = await getWeb3();

      // Use web3 to get the user's accounts.
      const accounts = await web3.eth.getAccounts();

      // Get the contract instance.
      const Contract = truffleContract(SimpleStorageContract);
      Contract.setProvider(web3.currentProvider);
      const instance = await Contract.deployed();

      // Set web3, accounts, and contract to the state, and then proceed with an
      // example of interacting with the contract's methods.
      this.setState({ web3, accounts, contract: instance }, this.runExample);
    } catch (error) {
      // Catch any errors for any of the above operations.
      alert(
        `Failed to load web3, accounts, or contract. Check console for details.`
      );
      console.log(error);
    }
  };

  runExample = async () => {
    const { accounts, contract } = this.state;

    // Stores a given value, 5 by default.
    await contract.set(5, { from: accounts[0] });

    // Get the value from the contract to prove it worked.
    const response = await contract.get();

    // Update state with the result.
    this.setState({ storageValue: response.toNumber() });
  };

  render() {
    if (!this.state.web3) {
      return <div>Loading Web3, accounts, and contract...</div>;
    }
    return (
      <div className="App">
        <h1>Good to Go!</h1>
        <p>Your Truffle Box is installed and ready.</p>
        <h2>Smart Contract Example</h2>
        <p>
          If your contracts compiled and migrated successfully, below will show
          a stored value of 5 (by default).
        </p>
        <p>
          Try changing the value stored on <strong>line 37</strong> of App.js.
        </p>
        <div>The stored value is: {this.state.storageValue}</div>
      </div>
    );
  }
}

export default App;
Truffle框架是一个用于以太坊智能合约开发的开发环境和工具集,Ganache则是一个用于本地测试以太坊智能合约的工具。下面是使用Truffle框架和Ganache网络进行智能合约部署的具体流程和代码。 1. 安装Truffle框架和Ganache网络 首先需要在本地安装Truffle框架和Ganache网络。可以使用npm命令进行安装: ``` npm install -g truffle npm install -g ganache-cli ``` 2. 创建Truffle项目 使用Truffle框架创建一个新的项目: ``` truffle init ``` 这将会在当前目录下创建一个名为`truffle-config.js`的配置文件和一个名为`contracts`的合约目录。 3. 编写智能合约代码 在`contracts`目录下创建一个名为`MyContract.sol`的智能合约文件,并编写合约代码。例如,创建一个简单的存储合约: ``` pragma solidity ^0.8.0; contract MyContract { uint256 private value; function setValue(uint256 newValue) public { value = newValue; } function getValue() public view returns (uint256) { return value; } } ``` 4. 配置Truffle项目 在`truffle-config.js`文件中配置Truffle项目。首先需要指定要使用的网络,这里使用Ganache网络: ``` module.exports = { networks: { development: { host: "localhost", port: 8545, network_id: "*" } } }; ``` 5. 编译智能合约 使用Truffle框架编译智能合约: ``` truffle compile ``` 6. 部署智能合约 使用Truffle框架部署智能合约: ``` truffle migrate ``` 这将会将智能合约部署到Ganache网络上。 7. 与智能合约交互 现在可以使用Web3.js或其他以太坊客户端库与智能合约进行交互。以下是一个使用Web3.js与上一步中部署的存储合约进行交互的示例代码: ``` const Web3 = require('web3'); const web3 = new Web3('http://localhost:8545'); const myContract = new web3.eth.Contract([{"inputs":[],"stateMutability":"nonpayable","type":"constructor"},{"inputs":[{"internalType":"uint256","name":"newValue","type":"uint256"}],"name":"setValue","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"getValue","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"}], '0x1234567890123456789012345678901234567890'); myContract.methods.setValue(42).send({from: '0x1234567890123456789012345678901234567890'}) .then(() => myContract.methods.getValue().call()) .then(value => console.log(value)); ``` 这段代码首先创建了一个Web3实例,并连接到Ganache网络。然后创建了一个`myContract`实例,它表示上一步中部署的存储合约。最后使用`myContract`实例调用`setValue`方法将值设置为42,并使用`getValue`方法获取当前值并输出到控制台。
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