Lesson 13 getContractAt() without ABI?

[asserules]

I'm just wondering how the getContractAt() works since we're not actually giving it an ABI. We're only giving it our IWeth interface. Do they have the same ABI, if so why?

getWeth.js
const iWeth = await ethers.getContractAt( "IWeth", "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", deployer )

IWeth.sol
`// SPDX-License-Identifier: MIT
pragma solidity ^0.4.19;

interface IWeth {
function allowance(address owner, address spender) external view returns (uint256 remaining);

function approve(address spender, uint256 value) external returns (bool success);

function balanceOf(address owner) external view returns (uint256 balance);

function decimals() external view returns (uint8 decimalPlaces);

function name() external view returns (string memory tokenName);

function symbol() external view returns (string memory tokenSymbol);

function totalSupply() external view returns (uint256 totalTokensIssued);

function transfer(address to, uint256 value) external returns (bool success);

function transferFrom(
    address from,
    address to,
    uint256 value
) external returns (bool success);

function deposit() external payable;

function withdraw(uint256 wad) external;

}
`

[othaime-en]

Hey @asserules the ethers.getContractAt() method takes three parameters: The ABI, the contract address, and the signer. In this case, IWeth provides the ABI. Yes the interface and the real contract have the same ABI. In simple terms, the ABI is a collection of parts or fragments that specify how we interact with different functions and components of a contract. And that's what interfaces are for right? Interfaces give us the skeleton structure of the real contracts in terms of of its functions. So if you compile the interface and the contract you will get the same ABI.

[asserules]

I see, thanks!

[krakxn]

It is because we can use getContractAt() even without the ABI of the contract and that is what we are doing here (specifically, in two ways: one is via the name and other is via the ABI); the only compulsory parameter is the address (i.e. the second one), the signer is optional.