什么是托管智能合约？

托管是在两方存在的情况下持有资产（资产可以是货币、债券、股票）的第三方。当满足某些条件时，托管将释放资金。
例如，“A”是卖家，想卖掉他的车，“B”是买家，想买“A”的车，所以他们会联系持有资产的托管“C”（仲裁者），直到“ B”收到车。当满足此条件时，Escrow 会将资金释放给“A”。这解决了信任问题并防止了任何差异。
让我们使用 Solidity 语言为 Escrow 编写智能合约。
在这里，智能合约将持有该资产，该资产将在条件满足时释放。

Solidity

pragma solidity 0.6.0;     
   
// Defining a Contract
contract escrow{
  
    // Declaring the state variables
    address payable public buyer;
    address payable public seller;
    address payable public arbiter;
    mapping(address => uint) TotalAmount;
  
    // Defining a enumerator 'State'
    enum State{
         
        // Following are the data members
        awate_payment, awate_delivery, complete 
    }
  
    // Declaring the object of the enumerator
    State public state;
      
    // Defining function modifier 'instate'
    modifier instate(State expected_state){
          
        require(state == expected_state);
        _;
    }
  
   // Defining function modifier 'onlyBuyer'
    modifier onlyBuyer(){
        require(msg.sender == buyer || 
                msg.sender == arbiter);
        _;
    }
  
    // Defining function modifier 'onlySeller'
    modifier onlySeller(){
        require(msg.sender == seller);
        _;
    }
      
    // Defining a constructor
    constructor(address payable _buyer, 
                address payable _sender) public{
        
        // Assigning the values of the 
        // state variables
        arbiter = msg.sender;
        buyer = _buyer;
        seller = _sender;
        state = State.awate_payment;
    }
      
    // Defining function to confirm payment
    function confirm_payment() onlyBuyer instate(
      State.awate_payment) public payable{
      
        state = State.awate_delivery;
          
    }
      
    // Defining function to confirm delivery
    function confirm_Delivery() onlyBuyer instate(
      State.awate_delivery) public{
          
        seller.transfer(address(this).balance);
        state = State.complete;
    }
  
    // Defining function to return payment
    function ReturnPayment() onlySeller instate(
      State.awate_delivery)public{
        
         
       buyer.transfer(address(this).balance);
    }
      
}