ERC223 Token standard

[Dexaran]

ERC: 223
Title: Token standard
Author: Dexaran, dexaran820@gmail.com
Status: Draft
Type: ERC
Created: 5-03.2017
Resolution: https://github.com/Dexaran/ERC23-tokens
ERC20 compatible example: https://github.com/Dexaran/ERC23-tokens/blob/ERC20_compatible/ERC23_token.sol

Abstract

The following describes standard functions a token contract and contract working with specified token can implement to prevent accidentally sends of tokens to contracts and make token transactions behave like ether transactions.

Motivation

Problems of ERC20 that ERC223 will solve:

1. Impossibility of handling incoming transactions in receiver contract.
2. Tokens could be sent to contract that is not designed to work with tokens without handling and potentially could be lost. At least $72000 are lost at the moment. This problem is described here.
3. Token-transactions should match Ethereum ideology of uniformity. When a user needs to transfer his funds, he must always perform transfer. Doesn't matter is user depositing in contract or sending to an externally owned account.

Those will allow contracts to handle incoming token transactions and prevent accidentally sent tokens from being accepted by contracts.
For example decentralized exchange will no more need to force users to call approve at token contract then call deposit that is calling transferFrom taking allowed tokens. Token transaction will automatically be handled inside the exchange contract.

The most important here is a call of tokenFallback when performing a transaction to a contract.

Specification

Token
Contracts that work with tokens

Methods

NOTE: An important point is that contract developers must implement tokenFallback if they want their contracts to work with the specified tokens.

If the receiver does not implement the tokenFallback function, consider the contract is not designed to work with tokens, then the transaction must fail and no tokens will be transferred. An analogy with an Ether transaction that is failing when trying to send Ether to a contract that did not implement function() payable.

totalSupply

function totalSupply() constant returns (uint256 totalSupply)

Get the total token supply

name

function name() constant returns (string _name)

Get the name of token

symbol

function symbol() constant returns (string _symbol)

Get the symbol of token

decimals

function decimals() constant returns (uint8 _decimals)

Get decimals of token

balanceOf

function balanceOf(address _owner) constant returns (uint256 balance)

Get the account balance of another account with address _owner

transfer(address, uint, bytes)

function transfer(address _to, uint _value, bytes _data) returns (bool success)

function that is always called when someone wants to transfer tokens.
This function must transfer tokens and invoke the function tokenFallback (address, uint256, bytes) in _to, if _to is a contract. If the tokenFallback function is not implemented in _to (receiver contract), then the transaction must fail and the transfer of tokens should not occur.
If _to is an externally owned address, then the transaction must be sent without trying to execute tokenFallback in _to.
_data can be attached to this token transaction and it will stay in blockchain forever (requires more gas). _data can be empty.

NOTE: The recommended way to check whether the _to is a contract or an address is to assemble the code of _to. If there is no code in _to, then this is an externally owned address, otherwise it's a contract.

IMPORTANT: Token fallback function that will be called at receiver contract must be named tokenFallback and take parameters address, uint256, bytes. This function must have 0xc0ee0b8a signature.

transfer(address, uint)

function transfer(address _to, uint _value) returns (bool success)

Needed due to backwards compatibility reasons because of ERC20 transfer function doesn't have bytes parameter. This function must transfer tokens and invoke the function tokenFallback(address, uint256, bytes) in _to, if _to is a contract. If the tokenFallback function is not implemented in _to (receiver contract), then the transaction must fail and the transfer of tokens should not occur.

IMPORTANT: Token fallback function that will be called at receiver contract must be named tokenFallback and take parameters address, uint256, bytes. This function must have 0xc0ee0b8a signature.

Events

Transfer

event Transfer(address indexed _from, address indexed _to, uint256 _value, bytes _data)

Triggered when tokens are transferred.

Contract to work with tokens

function tokenFallback(address _from, uint _value, bytes _data)

A function to handle token transfers that is called from token contract when token holder is sending tokens. _from is a token sender, _value is amount of incoming tokens and _data is attached data similar to data in Ether transactions. Works like fallback function for Ether transactions and returns nothing.

NOTE: msg.sender will be a token-contract inside the tokenFallback function. It may be important to filter which tokens are sent (by token-contract address). The token sender (the person who initiated the token transaction) will be _from inside the tokenFallback function.

IMPORTANT: This function must be named tokenFallback and take parameters address, uint256, bytes to match the function signature 0xc0ee0b8a.

Recommended implementation

This is highly recommended implementation of ERC 223 token: https://github.com/Dexaran/ERC23-tokens/tree/Recommended

[Dexaran]

I want to leave it here for discussion in the future, if anyone has any questions / suggestions.

[realcodywburns]

Lgtm