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本篇内容介绍了"ERC20代币标准怎么实现"的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧!希望大家仔细阅读，能够学有所成!

pragma solidity ^0.4.20;// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.mdcontract NanToken { //Token //Methods //NOTE: Callers MUST handle false from returns (bool success). Callers MUST NOT assume that false is never returned! // 所有 returns (bool success) 的方法，都要考虑返回false的逻辑; //name //Returns the name of the token - e.g. "MyToken". // //OPTIONAL - This method can be used to improve usability, but interfaces and other contracts MUST NOT expect these values to be present. function name() view returns (string name); //symbol //Returns the symbol of the token.E.g. "HIX". // //OPTIONAL - This method can be used to improve usability, but interfaces and other contracts MUST NOT expect these values to be present. function symbol() view returns (string symbol); //decimals //Returns the number of decimals the token uses - e.g. 8, means to divide the token amount by 100000000 to get its user representation. // //OPTIONAL - This method can be used to improve usability, but interfaces and other contracts MUST NOT expect these values to be present. // 精度 function decimals() view returns (uint8 decimals); //totalSupply //Returns the total token supply. function totalSupply() view returns (uint256 totalSupply); //balanceOf //Returns the account balance of another account with address _owner. // 总量 function balanceOf(address _owner) view returns (uint256 balance); //transfer //Transfers _value amount of tokens to address _to, and MUST fire the Transfer event. The function SHOULD throw if the _from account balance does not have enough tokens to spend. // //Note Transfers of 0 values MUST be treated as normal transfers and fire the Transfer event. // 从当前地址转指定量到指定地址 // 若当前地址没有足够的余额，应该抛出异常 // 每次调用成功，哪怕数量是0，都必须触发 Transfer 事件; function transfer(address _to, uint256 _value) returns (bool success); //transferFrom //Transfers _value amount of tokens from address _from to address _to, and MUST fire the Transfer event. // //The transferFrom method is used for a withdraw workflow, allowing contracts to transfer tokens on your behalf. This can be used for example to allow a contract to transfer tokens on your behalf and / or to charge fees in sub- currencies. The function SHOULD throw unless the _from account has deliberately authorized the sender of the message via some mechanism. // //Note Transfers of 0 values MUST be treated as normal transfers and fire the Transfer event. // 用于提币逻辑; // 每次调用成功必须触发 Transfer 事件;哪怕数量是0; function transferFrom(address _from, address _to, uint256 _value) returns (bool success); //approve //Allows _spender to withdraw from your account multiple times, up to the _value amount. If this function is called again it overwrites the current allowance with _value. // //NOTE : To prevent attack vectors like the one described here[https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh5DYKjA_jp-RLM/] and discussed here[https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729], clients SHOULD make sure to create user interfaces in such a way that they set the allowance first to 0 before setting it to another value for the same spender. THOUGH The contract itself shouldn't enforce it, to allow backwards compatibility with contracts deployed before // 允许指定的地址 分一次或多次从当前地址提币;若再次调用此方法，则重置数量 // 为避免攻击，客户端实现时应该先向某地址设置数量为0，再给相同的地址设置数量为 实际的数量; // 这为了向后兼容之前部署的合约,虽然不是强制要求 function approve(address _spender, uint256 _value) returns (bool success); //allowance //Returns the amount which _spender is still allowed to withdraw from _owner. // 查询 owner 授权给 spender 的剩余提币数量 function allowance(address _owner, address _spender) view returns (uint256 remaining); //Events //Transfer //MUST trigger when tokens are transferred, including zero value transfers. // //A token contract which creates new tokens SHOULD trigger a Transfer event with the _from address set to 0x0 when tokens are created. // token 被 成功 transfer 后，需要触发Transfer 事件，哪怕数量为0; // 当创建一个新的token后，应该触发Transfer 事件， event Transfer(address indexed _from, address indexed _to, uint256 _value); //Approval //MUST trigger on any successful call to approve(address _spender, uint256 _value). // 每次approve方法被成功调用后，都必须触发 Approval事件; event Approval(address indexed _owner, address indexed _spender, uint256 _value)};}"ERC20代币标准怎么实现"的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注网站，小编将为大家输出更多高质量的实用文章!

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