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Get Started With Developing In Ethereum - ERC-20

  • Familiarise yourself with the ERC-20 fungible token standard
  • Deploy your own ERC-20 token contract on the Ethereum Sepolia testnet
  • Interact with your own ERC-20 token contract

Table Of Contents


What is ERC-20?

The ERC-20 fungible token standard at https://eips.ethereum.org/EIPS/eip-20, originally proposed in Nov 2015 and finalised in Apr 2018, specifies a set of functions and events a smart contract must implement to be ERC-20 compliant.

FixedSupplyToken.sol

Following are snippets from a simple ERC-20 compliant fixed supply token contract, from contracts/FixedSupplyToken.sol.

The following IERC20 interface specifies the events and functions required for a smart contract to be compliant with https://eips.ethereum.org/EIPS/eip-20.

interface IERC20 {
    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed owner, address indexed spender, uint tokens);

    function name() external view returns (string memory);
    function symbol() external view returns (string memory);
    function decimals() external view returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint balance);
    function allowance(address owner, address spender) external view returns (uint remaining);

    function transfer(address to, uint tokens) external returns (bool success);
    function approve(address spender, uint tokens) external returns (bool success);
    function transferFrom(address from, address to, uint tokens) external returns (bool success);
}

The following FixedSupplyToken contract implements the ERC-20 interface above.

Note that the Solidity compiler automatically generates the getter functions for public variables: name(), symbol(), decimals(), balanceOf(owner) and allowance(owner, spender).

contract FixedSupplyToken is IERC20 {
    string constant public symbol = "HIHIHI";
    string constant public name = unicode"Hi 👋, Hi 👋, Hi 👋";
    uint8 constant public decimals = 18;
    uint constant public _totalSupply = 1_000_000_000_000_000_000_000_000; // 1,000,000.000000000000000000

    // owner => tokens
    mapping(address => uint) public balanceOf;
    // owner => spender => tokens
    mapping(address => mapping(address => uint)) public allowance;

    constructor() {
        balanceOf[msg.sender] = _totalSupply;
        emit Transfer(address(0), msg.sender, _totalSupply);
    }
    function totalSupply() external view override returns (uint) {
        return _totalSupply - balanceOf[address(0)];
    }
    function transfer(address to, uint tokens) external override returns (bool success) {
        balanceOf[msg.sender] -= tokens;
        balanceOf[to] += tokens;
        emit Transfer(msg.sender, to, tokens);
        return true;
    }
    function approve(address spender, uint tokens) external override returns (bool success) {
        allowance[msg.sender][spender] = tokens;
        emit Approval(msg.sender, spender, tokens);
        return true;
    }
    function transferFrom(address from, address to, uint tokens) external override returns (bool success) {
        balanceOf[from] -= tokens;
        allowance[from][msg.sender] -= tokens;
        balanceOf[to] += tokens;
        emit Transfer(from, to, tokens);
        return true;
    }
}

Screenshots below can be reproduced using the contract address 0x1e5df6db242d07cc40a37b634022c02f73a74d59 on the page https://bokkypoobah.github.io/GetStartedWithDevelopingInEthereum/, in a web3 enabled web browser.


Deploy Your Own ERC-20 Token Contract


Interact With Your Own ERC-20 Token Contract



Enjoy!

(c) BokkyPooBah / Bok Consulting Pty Ltd 2024. The MIT Licence.