自學以太坊智能合約，一知半解之下碰到很多問題，遂記錄下，方便以后查找，
第一個智能合約（Faucet）
觀看的B站尚硅谷的深入掌握以太坊核心技術-智能合約入門，仿著寫個水龍頭的智能合約
// Version of Solidity compiler this program was written for
pragma solidity ^0.4.19;
// Our first contract is a faucet!
contract Faucet {
// Give out ether to anyone who asks
function withdraw(uint withdraw_amount) public {
// Limit withdrawal amount
require(withdraw_amount <= 100000000000000000);
// Send the amount to the address that requested it
msg.sender.transfer(withdraw_amount);
}
// Accept any incoming amount
function () public payable {}
}
編譯通過：
但是該學習視頻已經是兩年前的了，用的編譯版本比較舊，remix上的例子里，版本都是
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0
那就試著改一下版本，發現開始報錯：
ParserError: Expected a state variable declaration. If you intended this as a fallback function or a function to handle plain ether transactions, use the "fallback" keyword or the "receive" keyword instead.
--> contracts/Faucet.sol:14:32:
|
14 | function () public payable {}
| ^
這是因為在0.6.0的版本更新中
所以我們需要對應下
發現有回退，就要有接收，那就再增加一下receive方法
編譯后發現還剩下一個問題，仔細看一下，發現
0.5.0版本中
0.6.0版本中
0.8.0版本中
由此可知，目前msg.sender已經不是address payable了，需要自己另外轉一下
編譯通過，合約處可以選擇Faucet合約了，語法修改完成，
最終改成如下代碼：
// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;
/**
* @title Faucet
* @dev Our first contract is a faucet!
*/
contract Faucet {
// Give out ether to anyone who asks
function withdraw(uint withdraw_amount) public {
// Limit withdrawal amount
require(withdraw_amount <= 100000000000000000);
// Send the amount to the address that requested it
payable(msg.sender).transfer(withdraw_amount);
}
// Accept any incoming amount
fallback () payable external {}
receive () payable external {}
}
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標籤：區塊鏈