Описание изменений

backend/contracts/MyContract.sol

@@ -1,27 +1,18 @@
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.0;
 
-contract MyContract {
-    address public owner;
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
+
+contract MyContract is Ownable, ReentrancyGuard {
     uint256 public price;
     
     event Purchase(address buyer, uint256 amount);
 
     constructor() {
-        owner = msg.sender;
         price = 0.01 ether; // Начальная цена 0.01 ETH
     }
 
-    modifier onlyOwner() {
-        require(msg.sender == owner, "Only owner can call this function");
-        _;
-    }
-
-    function setOwner(address newOwner) public onlyOwner {
-        require(newOwner != address(0), "New owner cannot be zero address");
-        owner = newOwner;
-    }
-
     function setPrice(uint256 newPrice) public onlyOwner {
         price = newPrice;
     }
@@ -30,12 +21,13 @@ contract MyContract {
         return price;
     }
 
-    function purchase(uint256 amount) public payable {
+    function purchase(uint256 amount) public payable nonReentrant {
         require(msg.value == price * amount, "Incorrect payment amount");
         emit Purchase(msg.sender, amount);
     }
 
-    function withdraw() public onlyOwner {
-        payable(owner).transfer(address(this).balance);
+    function withdraw() public onlyOwner nonReentrant {
+        (bool success, ) = owner().call{value: address(this).balance}("");
+        require(success, "Transfer failed");
     }
 }