Write down the permission
allowance is a mapping of a mapping: owner, then spender, then how much.
Fill in approve:
allowance[msg.sender][spender] = amount; emit Approval(msg.sender, spender, amount);
Nothing moves. You are recording a permission, and the token has not left your balance.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
contract Token {
uint256 public totalSupply;
mapping(address => uint256) public balanceOf;
mapping(address => mapping(address => uint256)) public allowance;
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);
constructor() {
totalSupply = 1000;
balanceOf[msg.sender] = totalSupply;
}
function approve(address spender, uint256 amount) external returns (bool) {
return true;
}
function transferFrom(address from, address to, uint256 amount) external returns (bool) {
return true;
}
}
Goals
The contract compiles
nothing to compile yet
Emit `Approval`
the contract has not run yet
Contract storage
Write a contract and it will deploy itself here.