Interfaces: IERC20

Typical implementation of interface, where we pass an address into an interface object.

IERC20 public immutable wmdToken;    

constructor(address wmdToken_){
        wmdToken = IERC20(wmdToken_);
    }

• can make the parameter of the constructor as IERC20 this will save the explicit conversion that you are doing.

IERC20 public immutable wmdToken;    

///@param wmdToken_ contract address
    constructor(IERC20 wmdToken_){
        wmdToken = wmdToken_;
    }

Why

By passing an address into an interface, it serves as a pointer to the actual contract allowing us to call the functions declared within the interface.

• since compiling the interface will provide us with the function signatures of the contract - which are needed to make function calls.

However, the point here is that the parameter is only considered an IERC20 in the scope of the compiler. Once the bytecode is generated, the parameter will be an address for purposes of type checking.

Meaning:

• before compilation -> IERC20 wmdToken_ is treated of type IERC20.

• after compilation -> IERC20 wmdToken_ will be compiled as => IERC20(address(wmdToken))

  • wmdToken = wmdToken_; then simply becomes the assignment like so:

    • wmdToken = ERC20(address(wmdToken))

If you have another contract that calls this constructor, and you compile both together, they both need to use IERC20.

If you compile them separately and deploy them, one can use IERC20 and the other an address.