Описание изменений

backend/contracts/MyContract.sol

@@ -3,9 +3,13 @@ pragma solidity ^0.8.0;
 
 contract MyContract {
     address public owner;
+    uint256 public price;
+    
+    event Purchase(address buyer, uint256 amount);
 
     constructor() {
         owner = msg.sender;
+        price = 0.01 ether; // Начальная цена 0.01 ETH
     }
 
     modifier onlyOwner() {
@@ -17,4 +21,21 @@ contract MyContract {
         require(newOwner != address(0), "New owner cannot be zero address");
         owner = newOwner;
     }
+
+    function setPrice(uint256 newPrice) public onlyOwner {
+        price = newPrice;
+    }
+
+    function getPrice() public view returns (uint256) {
+        return price;
+    }
+
+    function purchase(uint256 amount) public payable {
+        require(msg.value == price * amount, "Incorrect payment amount");
+        emit Purchase(msg.sender, amount);
+    }
+
+    function withdraw() public onlyOwner {
+        payable(owner).transfer(address(this).balance);
+    }
 }