Creating ERC20 tokens on the Ethereum Test NetworkWithin the Ethereum blockchain, we can record transactions and run smart contracts. These things allow us to run DApps (decentralized applications) and which can support the running of the infrastructure in return for some payment (Ether). A DApp can also create tokens for new currencies, shares in a company or to prove the ownership of an asset. ERC-20 is a standard format for a Fungible Token and which can support the sharing, transfer and storage of tokens. These tokens are supported by the whole of the Ethereum infrastructure and can be easily traded. They support a number of mandatory functions [code]:
There are also a number of options:
So, let's create a token named "ENUToken", and use the tutorial sample from [here]. First, we open up remix.ethereum [here], and enter the following Solidy contract: pragma solidity ^0.4.24; // ---------------------------------------------------------------------------- // 'ENU Token' token contract // // Deployed to : 0xbB15B38e4ef6aF154b89A2E57E03Cd5cbD752233 // Symbol : ENUToken // Name : ENU Token // Total supply: 100000000 // Decimals : 18 // Based on https://github.com/bitfwdcommunity/Issue-your-own-ERC20-token/tree/master/contracts // ---------------------------------------------------------------------------- // Safe maths // ---------------------------------------------------------------------------- contract SafeMath { function safeAdd(uint a, uint b) public pure returns (uint c) { c = a + b; require(c >= a); } function safeSub(uint a, uint b) public pure returns (uint c) { require(b <= a); c = a - b; } function safeMul(uint a, uint b) public pure returns (uint c) { c = a * b; require(a == 0 || c / a == b); } function safeDiv(uint a, uint b) public pure returns (uint c) { require(b > 0); c = a / b; } } // ---------------------------------------------------------------------------- // 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); } // ---------------------------------------------------------------------------- // Contract function to receive approval and execute function in one call // // Borrowed from MiniMeToken // ---------------------------------------------------------------------------- contract ApproveAndCallFallBack { function receiveApproval(address from, uint256 tokens, address token, bytes data) public; } // ---------------------------------------------------------------------------- // Owned contract // ---------------------------------------------------------------------------- contract Owned { address public owner; address public newOwner; event OwnershipTransferred(address indexed _from, address indexed _to); constructor() public { owner = msg.sender; } modifier onlyOwner { require(msg.sender == owner); _; } function transferOwnership(address _newOwner) public onlyOwner { newOwner = _newOwner; } function acceptOwnership() public { require(msg.sender == newOwner); emit OwnershipTransferred(owner, newOwner); owner = newOwner; newOwner = address(0); } } // ---------------------------------------------------------------------------- // ERC20 Token, with the addition of symbol, name and decimals and assisted // token transfers // ---------------------------------------------------------------------------- contract BillToken is ERC20Interface, Owned, SafeMath { string public symbol; string public name; uint8 public decimals; uint public _totalSupply; mapping(address => uint) balances; mapping(address => mapping(address => uint)) allowed; // ------------------------------------------------------------------------ // Constructor // ------------------------------------------------------------------------ constructor() public { symbol = "ENUToken"; name = "ENU Token"; decimals = 18; _totalSupply = 100000000000000000000000000; balances[0xbB15B38e4ef6aF154b89A2E57E03Cd5cbD752233] = _totalSupply; emit Transfer(address(0), 0xbB15B38e4ef6aF154b89A2E57E03Cd5cbD752233, _totalSupply); } // ------------------------------------------------------------------------ // Total supply // ------------------------------------------------------------------------ function totalSupply() public constant returns (uint) { return _totalSupply - balances[address(0)]; } // ------------------------------------------------------------------------ // Get the token balance for account tokenOwner // ------------------------------------------------------------------------ function balanceOf(address tokenOwner) public constant returns (uint balance) { return balances[tokenOwner]; } // ------------------------------------------------------------------------ // Transfer the balance from token owner's account to to account // - Owner's account must have sufficient balance to transfer // - 0 value transfers are allowed // ------------------------------------------------------------------------ function transfer(address to, uint tokens) public returns (bool success) { balances[msg.sender] = safeSub(balances[msg.sender], tokens); balances[to] = safeAdd(balances[to], tokens); emit Transfer(msg.sender, to, tokens); return true; } // ------------------------------------------------------------------------ // Token owner can approve for spender to transferFrom(...) tokens // from the token owner's account // // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20-token-standard.md // recommends that there are no checks for the approval double-spend attack // as this should be implemented in user interfaces // ------------------------------------------------------------------------ function approve(address spender, uint tokens) public returns (bool success) { allowed[msg.sender][spender] = tokens; emit Approval(msg.sender, spender, tokens); return true; } // ------------------------------------------------------------------------ // Transfer tokens from the from account to the to account // // The calling account must already have sufficient tokens approve(...)-d // for spending from the from account and // - From account must have sufficient balance to transfer // - Spender must have sufficient allowance to transfer // - 0 value transfers are allowed // ------------------------------------------------------------------------ function transferFrom(address from, address to, uint tokens) public returns (bool success) { balances[from] = safeSub(balances[from], tokens); allowed[from][msg.sender] = safeSub(allowed[from][msg.sender], tokens); balances[to] = safeAdd(balances[to], tokens); emit Transfer(from, to, tokens); return true; } // ------------------------------------------------------------------------ // Returns the amount of tokens approved by the owner that can be // transferred to the spender's account // ------------------------------------------------------------------------ function allowance(address tokenOwner, address spender) public constant returns (uint remaining) { return allowed[tokenOwner][spender]; } // ------------------------------------------------------------------------ // Token owner can approve for spender to transferFrom(...) tokens // from the token owner's account. The spender contract function // receiveApproval(...) is then executed // ------------------------------------------------------------------------ function approveAndCall(address spender, uint tokens, bytes data) public returns (bool success) { allowed[msg.sender][spender] = tokens; emit Approval(msg.sender, spender, tokens); ApproveAndCallFallBack(spender).receiveApproval(msg.sender, tokens, this, data); return true; } // ------------------------------------------------------------------------ // Don't accept ETH // ------------------------------------------------------------------------ function () public payable { revert(); } // ------------------------------------------------------------------------ // Owner can transfer out any accidentally sent ERC20 tokens // ------------------------------------------------------------------------ function transferAnyERC20Token(address tokenAddress, uint tokens) public onlyOwner returns (bool success) { return ERC20Interface(tokenAddress).transfer(owner, tokens); } } When you create your own contract, make sure you change the public constructor() with: the symbol, the name, and the wallet ID: constructor() public { symbol = "ENUToken"; name = "ENU Token"; decimals = 18; _totalSupply = 100000000000000000000000000; balances[0xbB15B38e4ef6aF154b89A2E57E03Cd5cbD752233] = _totalSupply; emit Transfer(address(0), 0xbB15B38e4ef6aF154b89A2E57E03Cd5cbD752233, _totalSupply); } The wallet ID is the public ID of your wallet in Metamask. You thus need to change "0xbB15B38e4..33" or for your public ID on the test network. This will allow you to transfer the tokens into your wallet. Now we can compile the contract: Next, we will deploy to the Ropsten test network: After this, our contract will be shown as being pending deployment: It will take 10–15 minutes to deploy, but it can be speeded up by increasing the gas limit: Once deployed, we can view the contract details: And can then view the transaction for the contact [here]: And then view the contact [here]: Next, we select the Contract tab: And then select "Verify and Publish" and enter the details of the compiler version (v0.4.26): We then need to copy-and-pasete the contract code into the Source Code text box: After less than 45 seconds, the contract will be approved: When the contact is run there is a constructor to transfer the tokens to the wallet we have defined (and who will be the owner of the token). We can now go back to the wallet which is specified, to see if the tokens have been transferred: Next, we can transfer the tokens into our wallet, by defining the contract address: We will now have our new tokens in the wallet: And with: We can now transfer the cryptocurrency to another wallet: We can view the ENUToken: [here]: |