[英]Call and access smart contract function through web3.js?
我需要知道如何通過 web3.js 將這些方法調用到我的前端,它在反應中以及結構數據中。
// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;
struct customer {
uint256 amount;
}
contract Lottery {
address payable public admin;
address payable[] public add;
mapping(address => customer) public data;
function getBalance() public view onlyOwner returns (uint256) {
return address(this).balance/1 ether;
}
function getter() view public returns (uint)
{
return add.length;
}
這是我正在使用的 React 代碼,但我無法調用其他函數(數組長度)
useEffect(()=>{
const getMemebers=async()=>{
const admin=await web3Api.contract.admin({
from:account
});
setAccount(admin);
}
web3Api.contract && getMemebers();
},[web3Api.web3])
假設您在 src 文件夾中設置了 web3.js 文件,我看到的唯一問題是您在 useEffect 中調用異步函數,這總是一個壞主意。
相反,您可以定義一個不同的異步函數並通常在 useEffect 中調用它。 如果您為其分配任何狀態,它將為您刷新 dom。 我沒有足夠的信息來提供更好的解決方案,但我正在添加我編寫的類似代碼並且有效
import { useState, useEffect } from 'react';
import './App.css';
import web3 from './web3';
import Lottery from './lottery';
function App() {
const [manager, setManager] = useState('');
const [players, setPlayers] = useState([]);
const [balance, setBalance] = useState('0');
const [value, setValue] = useState('');
const [message, setMessage] = useState('');
const [account, setAccount] = useState('');
async function setInitials(){
let address = await Lottery.methods.manager().call();
let playerList = await Lottery.methods.getPlayers().call();
let contractBalance = await web3.eth.getBalance(Lottery.options.address);
let accounts = await web3.eth.getAccounts();
setAccount(accounts[0]);
setManager(address);
setPlayers(playerList);
setBalance(web3.utils.fromWei(contractBalance, 'ether'));
}
const enterContract = async (e) => {
try {
e.preventDefault();
setMessage('Waiting for success of transaction...')
let accounts = await web3.eth.getAccounts();
await Lottery.methods.enter().send({
from: accounts[0],
value: web3.utils.toWei(value, 'ether')
})
setMessage('Transaction successful !!!')
setValue('');
setInitials();
} catch (error) {
setMessage(`Transaction failed: ${error.message}`)
}
}
const pickWInner = async () => {
try {
setMessage('Picking Winner');
let accounts = await web3.eth.getAccounts();
await Lottery.methods.pickWinner().send({
from: accounts[0]
})
let winner = await Lottery.methods.getWinner().call();
setMessage(`Winner is ${winner}. Congratulations!!`)
setInitials();
} catch (error) {
setMessage(`Failed to pick winner: ${error.message}`)
}
}
useEffect(() => {
setInitials();
// eslint-disable-next-line react-hooks/exhaustive-deps
}, [])
return (
<div className="App">
<h1>Lottery App</h1>
<p>This contract is managed by: {manager}</p>
<p>Number of players participated: {players.length}</p>
{
players.length > 0
?
<ul>List of players currently in Contract:
{players.map((player, index) => {
return <li key={index}>{player}</li>
})}
</ul>
:
<></>
}
<p>Total balance up for Grab: {balance} ether</p>
<hr />
<form onSubmit={enterContract}>
<h3>Want to try your luck?</h3>
<p>Enter amouth of ether you want to put in</p>
<input
placeholder='Min 0.01 Ether'
value={value}
onChange={e => setValue(e.target.value)}
/>
<button type='Submit'>Enter</button>
</form>
{
account === manager
?
<>
<hr />
<h2>Pick a Winner</h2>
<button onClick={pickWInner}>Pick Winner</button>
</>
:
<></>
}
<h1>{message}</h1>
</div>
);
}
export default App;
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