IERC20 vs ERC20

[TimeKeyRoll]

I am bit confused about them. As i understand IERC20 is an interface and could be used to create a tokenContract like this -- https://github.com/MasterofBlockchain/hardhat-erc20-fcc/blob/master/contracts/IERC20.sol

But with the help of ERC20 we could also create a tokenContract. like this--

pragma solidity ^0.8.7;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
contract OurToken is ERC20 {
    constructor(uint256 initialSupply) ERC20("OurToken", "OT") {
        _mint(msg.sender, initialSupply);
    }
}

So what makes them different to each other? And How do we know what Contract to use?

[othaime-en]

Hey @MasterofBlockchain IERC20 is the universal interface to be used when developing ERC20 standard tokens while ERC20 is the implementation of this interface. So you could either import ERC20 and inherit it or the best way would be to import the IERC20 interface and inherit it instead. Whatever you are comfortable with.

[TimeKeyRoll]

Absolutely! I mean i understand the difference but since they offer same kinda functions how do i know which one to choose? Since you said based on my comfort I can choose any of them. But As i have figured interface does not let us have stateVaribale or constructor.How we gonna fix that while using IERC20?
If they both are same then what makes them different from each other?

[krakxn]

Context on Interfaces (understand these rules):

As the functions implemented must be declared external, they are primarily used in other contracts because implementing functions manually in every other contract is redundant when you can just use a common interface.

E.g. Let's assume we have Contract A, B, C and Interface Z. A, B and C have a common function (literally the same) and therefore, will be redundant. It is much easier, cleaner (concise) and modular to implement that common function in Z, and then letting A, B and C inherit Z to use that common function.

Another simple analogy is

we do not have to know what is going on, and can just implement the functionality ("turns the light on") it provides.

Good read: https://medium.com/coinmonks/solidity-tutorial-all-about-interfaces-f547d2869499

[TimeKeyRoll]

Cool man! Very nicely Explained.
still left with a last question lol
if ERC20 is already have interface of ierc20 then we must be using only ERC20 for contract creation.
because there is no point for us to use IERC20 because ERC20 already have that interface. right?

[krakxn]

"if ERC20 is already have interface of ierc20 then we must be using only ERC20 for contract creation." Yes, that is correct as long as the contract itself inherits (uses) the interface by the is keyword.

"because there is no point for us to use IERC20 because ERC20 already have that interface." As ERC20 inherits (uses) the interface IERC20, we indeed are using it in a way--that is precisely what it is used for (i.e. after inheriting, we can implement whichever functions are necessary included in the IERC20 interace).

[TimeKeyRoll]

@krakxn In lesson-12 We have ManualToken. Is it ERC20 standards token written in pieces to understand ? And is it same as "@openzeppelin/contracts/token/ERC20/ERC20.sol"; this?

[krakxn]

@MasterofBlockchain Going by sheer memory here, so please verify it by yourself too. I am pretty sure that we just copy pasted the code in ManualToken from ERC20.sol, with the only changes being the constructor (so that we can change the name as per our liking).

[TimeKeyRoll]

lol so it is as same as 10=10.0