ERC20 Token Development

Circle Layer Blockchain is fully compatible with the ERC20 standard, allowing developers to create and deploy standard-compliant tokens seamlessly.

ERC20 Standard Interface

Circle Layer supports the complete ERC20 interface with all standard functions and events:

// ----------------------------------------------------------------------------
// ERC Token Standard #20 Interface
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md
// ----------------------------------------------------------------------------
contract ERC20Interface {
    function totalSupply() public constant returns (uint);
    function balanceOf(address tokenOwner) public constant returns (uint balance);
    function allowance(address tokenOwner, address spender) public constant returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}

Implementation Example

Basic ERC20 Token Contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract MyToken {
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;
    
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    
    constructor(
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        uint256 _totalSupply
    ) {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        totalSupply = _totalSupply * 10**_decimals;
        balanceOf[msg.sender] = totalSupply;
        emit Transfer(address(0), msg.sender, totalSupply);
    }
    
    function transfer(address to, uint256 value) public returns (bool) {
        require(balanceOf[msg.sender] >= value, "Insufficient balance");
        balanceOf[msg.sender] -= value;
        balanceOf[to] += value;
        emit Transfer(msg.sender, to, value);
        return true;
    }
    
    function approve(address spender, uint256 value) public returns (bool) {
        allowance[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }
    
    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        require(balanceOf[from] >= value, "Insufficient balance");
        require(allowance[from][msg.sender] >= value, "Allowance exceeded");
        
        balanceOf[from] -= value;
        balanceOf[to] += value;
        allowance[from][msg.sender] -= value;
        
        emit Transfer(from, to, value);
        return true;
    }
}

Deployment Guide

Using Remix IDE

1. Open Remix: Navigate to remix.ethereum.org
2. Create Contract: Create a new file with your ERC20 contract
3. Compile: Select Solidity compiler version 0.8.0 or higher
4. Deploy:
   • Select "Injected Web3" environment
   • Ensure MetaMask is connected to Circle Layer testnet
   • Set constructor parameters
   • Click "Deploy"

Using Hardhat

Project Setup

npm install --save-dev hardhat @nomiclabs/hardhat-ethers ethers
npx hardhat init

Hardhat Configuration

// hardhat.config.js
require("@nomiclabs/hardhat-ethers");

module.exports = {
  solidity: "0.8.19",
  networks: {
    circlelayer: {
      url: "https://testnet-rpc.circlelayer.com",
      chainId: 28525,
      accounts: [process.env.PRIVATE_KEY]
    }
  }
};

Deployment Script

// scripts/deploy.js
async function main() {
  const [deployer] = await ethers.getSigners();
  
  console.log("Deploying with account:", deployer.address);
  console.log("Account balance:", (await deployer.getBalance()).toString());
  
  const Token = await ethers.getContractFactory("MyToken");
  const token = await Token.deploy(
    "My Token",      // name
    "MTK",           // symbol
    18,              // decimals
    1000000          // total supply (1M tokens)
  );
  
  await token.deployed();
  console.log("Token deployed to:", token.address);
}

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

Deploy Command

npx hardhat run scripts/deploy.js --network circlelayer

Advanced Features

Mintable Tokens

contract MintableToken is ERC20Interface {
    address public owner;
    
    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }
    
    function mint(address to, uint256 amount) public onlyOwner {
        totalSupply += amount;
        balanceOf[to] += amount;
        emit Transfer(address(0), to, amount);
    }
}

Burnable Tokens

function burn(uint256 amount) public {
    require(balanceOf[msg.sender] >= amount, "Insufficient balance");
    balanceOf[msg.sender] -= amount;
    totalSupply -= amount;
    emit Transfer(msg.sender, address(0), amount);
}

Pausable Tokens

contract PausableToken is ERC20Interface {
    bool public paused = false;
    address public owner;
    
    modifier whenNotPaused() {
        require(!paused, "Token is paused");
        _;
    }
    
    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }
    
    function pause() public onlyOwner {
        paused = true;
    }
    
    function unpause() public onlyOwner {
        paused = false;
    }
    
    function transfer(address to, uint256 value) public whenNotPaused returns (bool) {
        // transfer logic
    }
}

Token Verification

Contract Verification on Explorer

1. Navigate to explorer-testnet.circlelayer.com
2. Search for your contract address
3. Click "Verify Contract"
4. Submit source code and constructor parameters

Metadata Standards

contract MyToken {
    // Standard metadata
    string public name = "My Token";
    string public symbol = "MTK";
    uint8 public decimals = 18;
    
    // Optional metadata
    string public website = "https://mytoken.com";
    string public github = "https://github.com/mytoken/token";
    
    // Token logo (IPFS hash)
    string public logoURI = "ipfs://QmTokenLogo...";
}

Testing Your Token

Unit Tests with Hardhat

// test/MyToken.test.js
const { expect } = require("chai");

describe("MyToken", function () {
  let token;
  let owner;
  let addr1;
  let addr2;

  beforeEach(async function () {
    [owner, addr1, addr2] = await ethers.getSigners();
    const Token = await ethers.getContractFactory("MyToken");
    token = await Token.deploy("Test Token", "TEST", 18, 1000000);
    await token.deployed();
  });

  it("Should have correct initial supply", async function () {
    expect(await token.totalSupply()).to.equal(ethers.utils.parseEther("1000000"));
    expect(await token.balanceOf(owner.address)).to.equal(ethers.utils.parseEther("1000000"));
  });

  it("Should transfer tokens between accounts", async function () {
    await token.transfer(addr1.address, ethers.utils.parseEther("100"));
    expect(await token.balanceOf(addr1.address)).to.equal(ethers.utils.parseEther("100"));
  });

  it("Should handle approvals correctly", async function () {
    await token.approve(addr1.address, ethers.utils.parseEther("100"));
    expect(await token.allowance(owner.address, addr1.address)).to.equal(ethers.utils.parseEther("100"));
  });
});

Run Tests

npx hardhat test

Integration with DeFi

Adding Liquidity to DEX

// Example: Adding token to Circle Layer DEX
const tokenContract = new ethers.Contract(tokenAddress, tokenABI, signer);
const dexRouter = new ethers.Contract(routerAddress, routerABI, signer);

// Approve tokens for DEX
await tokenContract.approve(routerAddress, ethers.utils.parseEther("1000"));

// Add liquidity
await dexRouter.addLiquidityETH(
  tokenAddress,
  ethers.utils.parseEther("1000"),  // token amount
  0,                                // min token amount
  0,                                // min ETH amount
  owner.address,                    // to
  Math.floor(Date.now() / 1000) + 3600  // deadline
);

Best Practices

Security Considerations

1. Use OpenZeppelin: Consider using OpenZeppelin contracts
2. Audit Smart Contracts: Have contracts audited before mainnet deployment
3. Test Thoroughly: Comprehensive testing on testnet
4. Handle Edge Cases: Check for integer overflow/underflow
5. Access Control: Implement proper owner/admin controls

Gas Optimization

1. Efficient Storage: Use appropriate data types
2. Batch Operations: Combine multiple operations when possible
3. Event Optimization: Use indexed parameters judiciously
4. Code Optimization: Remove unnecessary computations

Token Economics

1. Supply Management: Plan token distribution carefully
2. Inflation/Deflation: Consider burn mechanisms
3. Utility: Ensure tokens have clear use cases
4. Governance: Plan for future governance needs

Common Issues & Solutions

Deployment Failures

Issue: "Gas estimation failed" Solution: Increase gas limit or check for contract errors

Issue: "Nonce too low" Solution: Reset MetaMask account or check pending transactions

Transfer Issues

Issue: "Insufficient balance" Solution: Verify account balance and token amount

Issue: "Allowance exceeded" Solution: Check and increase allowance if needed

References

• EIP-20 Standard: https://eips.ethereum.org/EIPS/eip-20
• OpenZeppelin Contracts: https://github.com/OpenZeppelin/openzeppelin-contracts/tree/master/contracts/token/ERC20
• Circle Layer Testnet Explorer: https://explorer-testnet.circlelayer.com
• Circle Layer Faucet: https://faucet.circlelayer.com

ERC20 token development on Circle Layer provides developers with a fast, low-cost environment for creating and deploying standard-compliant tokens with full Ethereum ecosystem compatibility.