Lesson 12 - documentation for ERC20 constructor?

[funkycapra]

Apologies in advance if this turns out to have a trivial or ridiculously obvious answer, but . . .

How does one determine the parameters needed for the OurToken contract constructor constructor(uint256 initialSupply) ERC20("OurToken", "OT")? (I am not talking about the parameter values, but the parameters themselves.) I realize that we are inheriting from openzeppelin's ERC20 implementation, but there is no constructor in the openzeppelin ERC20.sol code. I understand the structure of a constructor for a contract that has parents - but I am wondering how we know that initialSupply is needed as a parameter in the first part of the linearization list and how we should know that the name and symbol parameters are to be passed in through a modifier to the derived/child portion of the constructor parameter linearization list. Do we somehow infer what the constructor should be based on the EIP-20 spec and openzeppelin's implemenation?

[alymurtazamemon]

@PatrickAlphaC

[krakxn]

The code snippet for the entire constructor please.

[funkycapra]

contract code from @PatrickAlphaC repo for this lesson:

// contracts/OurToken.sol
// SPDX-License-Identifier: MIT
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);
  }
}

Again - I am not having an issue getting this to run - my question is more along the lines of how did @PatrickAlphaC know to write this constructor as he did when the openzeppelin ERC20.sol code does not have a constructor block.

[krakxn]

Here it is:

/**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

Taken from ERC20.sol—it conforms to what Patrick has done (w/ the correct order precedence).

Also, it is important to note that this is necessary because OurToken inherits (i.e. "is a") ERC20. Thereby initializing with the parameters "OurToken" and "OT"

[funkycapra]

Here it is:

/**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

Taken from ERC20.sol—it conforms to what Patrick has done (w/ the correct order precedence).

Also, it is important to note that this is necessary because OurToken inherits (i.e. "is a") ERC20. Thereby initializing with the parameters "OurToken" and "OT"

Thank you @krakxn - This is the answer. I was on ethereum.org's EIP-20 page and clicked the link to ERC20.sol on that page which goes to a much older version of the ERC20.sol file (github commit is from Sep 2018) and that older version apparently does not have a constructor explicitly defined in the code which is why I was not seeing a constructor. Sorry.

[krakxn]

All good, all the best!