即使函数声明为payable，得到此错误:如果发送值，则应支付被调用的函数。

Question

虽然函数purchaseProduct()声明为even，但我还不知道为什么会出现上述错误。我在Remix上尝试了这段代码，得到了这个错误。

VM错误:还原。还原事务已恢复到初始状态。注意:如果您发送值，则应支付被调用的函数，而您发送的值应小于当前余额。调试事务以获得更多信息。

除了purchaseProduct()函数之外，一切都很正常。我正在尝试从struct 'User‘、'Product’中获取数据，并在一个新的结构中(即“Order”)重新存储数据。

我已经使用require()进行了验证。在Remix上运行代码时：

1. 创建2个用户

1. 使用第一个用户创建产品，然后，

1. 使用第二用户的purchaseProduct

pragma solidity >=0.5.0;
pragma experimental ABIEncoderV2;

//Address: '0x7772B9117586b5F745bDb563a935E91b00449157'

contract Buyproduct{

    uint public orderCount = 0;
    mapping(uint => Order) public orders;

    uint public productCount = 0;
    mapping(uint => Product) public products;

    uint public userCount = 0;
    mapping(address => User) public users;

    struct Order {
        uint oid;
        address payable seller;
        address payable buyer;
      //  string timestamp;
        string status;
        uint pid;
        string location;
        uint quantitiy;
    }

    struct Product {
        uint pid;
        string name;
        uint price;
        address payable seller;

        string info;
        uint quantity;
    }

    struct User {
        uint uid;
        string name;
        uint role;
        address payable user;
        string location;
        bool created;
    }

    event ProductCreated(
        uint pid,
        string name,
        uint price,
        address payable seller,
        string info,
        uint quantity
    );

    event  UserCreated(
        uint uid,
        string name,
        uint role,
        address payable user,
        string location,
        bool created
    );

    event ProductPurchased(
        uint oid,
        address payable seller,
        address payable buyer,
        string status,
        uint pid,
        string location,
        uint quantity
    );

    event ReviewAdded(
        uint rid,
        address reviewer,
        uint pid,
        string review
    );

    function createUser(string memory _name, uint _role, string memory _location) public payable{
        //No repeated address
        require(users[msg.sender].created == false, 'User already created');
        //Increase userCount
        userCount++;
        //Add user
        users[msg.sender] = User(userCount, _name, _role, msg.sender, _location, true);
        //Trigger an event
        emit UserCreated(userCount, _name, _role, msg.sender, _location, true);
    }

    function createProduct(string memory _name, uint _price, string memory _info, uint _quantity) public payable {
        // Require a valid price
        require(_price > 0, 'Invalid Price');
        // Increment product count
        productCount ++;
        // Create the product
        products[productCount] = Product(productCount, _name, _price, msg.sender, _info, _quantity);
        // Trigger an event
        emit ProductCreated(productCount, _name, _price, msg.sender, _info, _quantity);
    }

    function purchaseProduct(uint _id, /*string memory timestamp,*/ uint _quantity) public payable {
        // Fetch the product
        Product memory _product = products[_id];
        // Fetch the owner
        address payable _seller = _product.seller;
        //Validate the buyer
        require(users[msg.sender].created == true, 'Unregistered user');
        // Make sure the product has a valid id
        require(_product.pid > 0 && _product.pid <= productCount, 'Invalid Product ID');
        // Require that there is enough Ether in the transaction
        require(msg.value >= _product.price, 'Not enough ether in Wallet');
        // Require that the buyer is not the seller
        require(_seller != msg.sender,'Invalid Purchase');
        //Incrmement orderCount
        orderCount++;
        // Transfer ownership to the buyer
        orders[orderCount] = Order(orderCount, _seller, msg.sender,/* ts,*/ 'Ordered', _product.pid, users[msg.sender].location, _quantity);
        //Reduce the quantity of the product
        _product.quantity -= _quantity;
        // Pay the contract by sending them Ether
        address payable wallet = address(uint160(address(this)));
        wallet.transfer(msg.value);
        // Trigger an event
        emit ProductPurchased(orderCount, _seller, msg.sender, /*timestamp,*/ 'Ordered', _product.pid, users[msg.sender].location, _quantity);
    }


}'''

Answer 1

    function createProduct(string memory _name, uint _price, string memory _info, uint _quantity) public payable {

这个函数的签名在醚中有_price。因此，尝试更改默认单位从卫乙醚，并发送适当的价格的产品。

我的在工作

[vm]from:0x4b0...4d2dbto:Buyproduct.purchaseProduct(uint256,uint256) 0x1df...bda71value:2000000000000000000 weidata:0xa04...00001logs:1hash:0x4e0...0d2b0

您也不需要显式地调用这些。

address payable wallet = address(uint160(address(this)));
wallet.transfer(msg.value);

合同余额将自动更新。您可以通过在合同上实现此功能来进行检查。

    function getBalance()
             public 
             view 
             returns(uint) {
                return address(this).balance;}