購買代幣功能在眾售智能合約中不起作用

我是乙太坊區塊鏈的新手。我創建了一個眾籌和 ERC20 智能合約並部署在 rinkeby 測試網路上。ERC20 代幣轉移功能執行良好。

但是當我檢查購買令牌功能的功能時。所以它執行成功。但是當我在https://rinkeby.etherscan.io/檢查它的輸出時。所以它顯示 0 代幣轉移。而且它不會在錢包上顯示代幣價格。

眾籌智能合約程式碼如下：-

pragma solidity ^0.4.2;

import "./DappToken.sol";

contract DappTokenSale {
   address admin;
   DappToken public tokenContract;
   uint256 public tokenPrice;
   uint256 public tokensSold;
   uint256 public decimals;


   event Sell(address _buyer, uint256 _amount);

   function DappTokenSale(DappToken _tokenContract, uint256 _tokenPrice) public {
       admin = msg.sender;
       tokenContract = _tokenContract;
       tokenPrice = _tokenPrice;
   }

   function multiply(uint x, uint y) internal pure returns (uint z) {
       require(y == 0 || (z = x * y) / y == x);
   }

   function buyTokens(address _receiver, uint256 _amount) public payable {
       _amount = msg.value;
       require(_receiver != address(0));
       require(_amount > 0);
       uint256 tokensToBuy = multiply(_amount, (10 ** decimals)) / 1 ether * tokenPrice;
       require(tokenContract.transfer(msg.sender, tokensToBuy));
       tokensSold += _amount;

       emit Sell(msg.sender, tokensToBuy);
   }

 // Ending Token DappTokenSale
   function endSale() public {
           // Require admin
           require (msg.sender == admin);

            // Transfer remaing DappToken to admin
           require(tokenContract.transfer(admin,tokenContract.balanceOf(this)));


           // Destroy Contract
           selfdestruct(admin);
   }
}

DappToken Solidity 程式碼：-

pragma solidity ^0.4.24;

/**
* The contractName contract does this and that...
*/

contract DappToken {
   // Name
   string public name = "DappToken";
   // Symbol
   string public symbol = 'DAPP';
   //standard
   string public standard = 'DApp Token v1.0';
   //Decimals
   uint256 public decimals = 18;
   //token price
   uint256 public tokenPrice = 2000; //1 eth = 2000 tokens

   uint256 public totalSupply;

   event Transfer(
       address indexed _form,
       address indexed _to,
       uint256 _value
       );

   event Approval(
           address indexed _owner,
           address indexed _spender,
           uint256 _value
       );


   mapping(address => uint256) public balanceOf;
   mapping(address => mapping (address => uint256)) public allowance;


//  function DappToken (uint256 _intialSupply) public {
//      balanceOf[msg.sender] = _intialSupply;
//      totalSupply = _intialSupply;
//      //allocate the intial supply
//
//  }
   constructor(uint256 _intialSupply) public
           {
               balanceOf[msg.sender] = _intialSupply;
               totalSupply = _intialSupply;
           }

   //Transfar
   function transfer(address _to,uint256 _value) public returns (bool success){
   // Exception if account does not enough
   require(balanceOf[msg.sender] >= _value);
   // Transfar the balance
   balanceOf[msg.sender] -= _value;
   balanceOf[_to] += _value; 

   // Transfar Event
   emit Transfer(msg.sender,_to,_value);

   // Return a boolean
   return true;
   } 

   // approve
   function approve(address _spender,uint256 _value) public returns (bool success){
       //allowence
       allowance[msg.sender][_spender] = _value;

       // Approve event
       emit Approval(msg.sender,_spender,_value);
            return true;

   }
   // transfer form
   function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
       require(_value <= balanceOf[_from]);
       require(_value <= allowance[_from][msg.sender]);
       // change the balance
       balanceOf[_from] -= _value;

       //update the balance
      balanceOf[_to] += _value; 

      allowance[_from][msg.sender] -= _value;

      emit Transfer(_from,_to,_value);


       return true;
   }
}

實際上我想購買這樣的代幣功能：-

1. 使用者輸入代幣數量（3 個乙太幣）。
2. 我設置代幣價格 1 ether= 2000 代幣。
3. 因此，當使用者輸入 3 個乙太幣時，他的帳戶中就會轉移 6000 個代幣。

所以我的查詢是：-

Query-1 :-為什麼購買代幣功能不會在接收者賬戶中發送 6000 代幣？

Query-1 :-我在智能合約程式碼中做錯了什麼？

我認為這應該是你的功能：

function buyTokens(address _receiver) public payable { 
uint256 _amount = msg.value; 
require(_receiver != address(0)); require(_amount > 0); 
uint256 tokensToBuy = multiply(_amount, (10 * decimals)) / 1 ether tokenPrice;
require(tokenContract.transfer(_receiver, tokensToBuy)); 
tokensSold += _amount; 

emit Sell(msg.sender, tokensToBuy); }

編輯：您可以通過Metamask檢查最終使用者收到的代幣數量。

引用自：https://ethereum.stackexchange.com/questions/60228