我用了两种方法，分别是test和test1
// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v3.0.0/contracts/token/ERC20/ERC20.sol";
contract MockERC20 is ERC20{
constructor(string memory _name, string memory _symbol) public ERC20(_name, _symbol) {
_mint(msg.sender, 100000000 * 10 ** 18);
}
}
contract Test{
ERC20 erc20;
constructor(ERC20 _erc20) public{
erc20 = _erc20;
}
function transferFrom(address _to,uint256 _amount) public{
erc20.transferFrom(msg.sender,_to,_amount);
}
}
contract Test1{
address erc20;
constructor(address _erc20) public{
erc20 = _erc20;
}
function transferFrom(address _to,uint256 _amount) public returns(bool){
bytes32 a = keccak256("transferFrom(address,address,uint256)");
bytes4 methodId = bytes4(a);
bytes memory b = abi.encodeWithSelector(methodId,msg.sender,_to,_amount);
(bool result,) = erc20.call(b);
return result;
}
}
