How to make a delegatecall to external ERC20 token's approve function?

Question

What I would like to do is something like this:

function testCall(uint amount) public virtual returns (bool) {
address tta = address(0xE7B6....);    
    
(bool success, bytes memory result) = tta.delegatecall(abi.encodeWithSignature("approve(address, uint256)", address(this), amount));
return success;
}

The token looks like this (has the approve function)

However, whenever the function is executed, it reverts with an error.

What am I doing wrong?

What I need to accomplish is to let the user approve the contract to make a transferFrom by executing the contract's testCall() function first.

Answer 1

You are adding a space in your function which is producing a different method signature.

> provider.eth.abi.encodeFunctionSignature('approve(address, uint256)')
0x8b069f2a

provider.eth.abi.encodeFunctionSignature('approve(address,uint256)')
0x095ea7b3

If you remove the space, it should work!