Interface in Solidity

Solidity Foundry Opcodes Security
3 min readFeb 14, 2022


Thanks to Alim.


We firstly deploy counter contract

Now deploy MyContract contract

You click the increment and then count button in counter contract

Now copy the counter contract’s address, in this sample, 0XAE0

and paste the incrementCounter button in MyContract contract.

Click it.

You can check the count situation in counter contract.

This is interface business.

ERC20 | IERC20

What does really Interface make Interface….

The main point of using interfaces ( or Abstract Contracts ) is to provide a customizable and re-usable approach for your contracts.

ERC20 is an implementation of the Interface defined in IERC20.

IERC20 defines function signatures without specifying behavior; the function names, inputs and outputs, but no process.

ERC20 inherits this Interface and is required to implement all the functions described or else the contract will not deploy.

If this is deployed, then we can safely say that all the functions described in the ERC20 Interface laid out in IERC20 have corresponding implementations in ERC20.

Look at IERC20 Interface :

Now look at ERC20

ERC20 inherits the IERC20 Interface

Do you want to see both of them in one picture ?

Come on

This is ERC20 an IERC20 business