- approve() is to give accountB an amount of token
- allowance() is for checking the approved amount. You have to specify relationship between accountA and accountB
- transferFrom() is to transfer the allowed amount
Last active
July 17, 2018 09:21
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Save Tanapruk/eed224e152d7913ca70fbaa8aadd139d to your computer and use it in GitHub Desktop.
erc20 token test inspired by https://medium.com/bitfwd/how-to-issue-your-own-token-on-ethereum-in-less-than-20-minutes-ac1f8f022793
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pragma solidity ^0.4.18; | |
// ---------------------------------------------------------------------------- | |
// 'Tanapruk' token contract | |
// | |
// Deployed to : 0xAe53EeAd0eE4c28FA838dAc87Cd6c0D9749Fb829 | |
// Symbol : TANAP | |
// Name : TANAP Token | |
// Total supply: 100000000 | |
// Decimals : 18 | |
// | |
// Enjoy. | |
// | |
// (c) by Moritz Neto with BokkyPooBah / Bok Consulting Pty Ltd Au 2017. The MIT Licence. | |
// ---------------------------------------------------------------------------- | |
// ---------------------------------------------------------------------------- | |
// 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 view returns (uint); | |
function balanceOf(address tokenOwner) public view returns (uint balance); | |
function allowance(address tokenOwner, address spender) public view 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 TanapToken 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 = "TANAP"; | |
name = "TANAP Token"; | |
decimals = 18; | |
_totalSupply = 100000000000000000000000000; | |
balances[0xAe53EeAd0eE4c28FA838dAc87Cd6c0D9749Fb829] = _totalSupply; | |
emit Transfer(address(0), 0xAe53EeAd0eE4c28FA838dAc87Cd6c0D9749Fb829, _totalSupply); | |
} | |
// ------------------------------------------------------------------------ | |
// Total supply | |
// ------------------------------------------------------------------------ | |
function totalSupply() public view returns (uint) { | |
return _totalSupply - balances[address(0)]; | |
} | |
// ------------------------------------------------------------------------ | |
// Get the token balance for account tokenOwner | |
// ------------------------------------------------------------------------ | |
function balanceOf(address tokenOwner) public view 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 view 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); | |
} | |
} |
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