Adding additional mutable variables in an ERC-20 Token Smart Contract (Extending ERC-20)

Question

I am having a question considering inheritance/extending of ERC-20 Token Smart Contracts.

I would like to add additional mutable variables to an ERC-20 token before the deployment on the Ethereum Mainnet.

Alongside the defined variables by the interface:

name (string),
symbol (string),
decimals (uint8),
totalSupply(uint8)

I would like to add additional mutable variables, which values could be changed after deployment through transactions. They would look something like this:

issuedSupply(uint8),
dedicatedManager(string)

I did not find an answer yet in the official specification references:

• https://ethereum.org/en/developers/docs/standards/tokens/erc-20/
• https://eips.ethereum.org/EIPS/eip-20

There are two similar questions:

• Extending ERC-721 with additional functionality
  • Says extending is generally possible
• Extending Issued ERC 20 Token
  • Says extending in ERC-20 is not possible after deployment, which makes sense.

So, to make my question complete:

Can I implement a smart contract, complying to the ERC-20 standard and having additional parameters which are publicly visible and which values can be changed after deployment through transactions?

Thanks a lot for having a look at my my question,

Kind regards

Answer 1

The smart contracts can be extended using the inheritance pattern and you can add additional fields on block storage if you want. You can also update these fields using a transaction. A sample would look like

contract ERC20FixedSupply is ERC20 {
    string public test;
    constructor() public {
        _mint(msg.sender, 1000);
    }
    function setTest(string memory _test) public {
       require( msg.sender == owner, "Should be owner" );
       test = _test;
    }
}

In the above example the setTest function can be used to set the custom variable test and ERC20FixedSupply is a ERC-20 Smart contract