Add chapter 4

code/celo101-code-chapter_4/4-1-edit-functions/marketplace.sol

@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.7.0 <0.9.0;
+
+interface IERC20Token {
+  function transfer(address, uint256) external returns (bool);
+  function approve(address, uint256) external returns (bool);
+  function transferFrom(address, address, uint256) external returns (bool);
+  function totalSupply() external view returns (uint256);
+  function balanceOf(address) external view returns (uint256);
+  function allowance(address, address) external view returns (uint256);
+
+  event Transfer(address indexed from, address indexed to, uint256 value);
+  event Approval(address indexed owner, address indexed spender, uint256 value);
+}
+
+contract Marketplace {
+
+    uint internal productsLength = 0;
+    address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
+
+    struct Product {
+        address payable owner;
+        string name;
+        string image;
+        string description;
+        string location;
+        uint price;
+        uint sold;
+    }
+
+    mapping (uint => Product) internal products;
+
+    function writeProduct(
+        string memory _name,
+        string memory _image,
+        string memory _description, 
+        string memory _location, 
+        uint _price
+    ) public {
+        uint _sold = 0;
+        products[productsLength] = Product(
+            payable(msg.sender),
+            _name,
+            _image,
+            _description,
+            _location,
+            _price,
+            _sold
+        );
+        productsLength++;
+    }
+
+    function readProduct(uint _index) public view returns (
+        address payable,
+        string memory, 
+        string memory, 
+        string memory, 
+        string memory, 
+        uint, 
+        uint
+    ) {
+        return (
+            products[_index].owner,
+            products[_index].name, 
+            products[_index].image, 
+            products[_index].description, 
+            products[_index].location, 
+            products[_index].price,
+            products[_index].sold
+        );
+    }
+
+    function buyProduct(uint _index) public payable  {
+        require(
+          IERC20Token(cUsdTokenAddress).transferFrom(
+            msg.sender,
+            products[_index].owner,
+            products[_index].price
+          ),
+          "Transfer failed."
+        );
+        products[_index].sold++;
+    }
+
+    function editProduct(uint _index, 
+        string memory _name,
+        string memory _image,
+        string memory _description, 
+        string memory _location, 
+        uint _price
+        ) public {
+        require(products[_index].owner == msg.sender, "You can not edit this product.");
+        products[_index].name = _name;
+        products[_index].image = _image;
+        products[_index].description = _description;
+        products[_index].location = _location;
+        products[_index].price = _price;
+    }
+
+    function getProductsLength() public view returns (uint) {
+        return (productsLength);
+    }
+}

code/celo101-code-chapter_4/4-2-delete-functions/marketplace.sol

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.7.0 <0.9.0;
+
+interface IERC20Token {
+  function transfer(address, uint256) external returns (bool);
+  function approve(address, uint256) external returns (bool);
+  function transferFrom(address, address, uint256) external returns (bool);
+  function totalSupply() external view returns (uint256);
+  function balanceOf(address) external view returns (uint256);
+  function allowance(address, address) external view returns (uint256);
+
+  event Transfer(address indexed from, address indexed to, uint256 value);
+  event Approval(address indexed owner, address indexed spender, uint256 value);
+}
+
+contract Marketplace {
+
+    uint internal productsLength = 0;
+    address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
+
+    struct Product {
+        address payable owner;
+        string name;
+        string image;
+        string description;
+        string location;
+        uint price;
+        uint sold;
+    }
+
+    mapping (uint => Product) internal products;
+
+    function writeProduct(
+        string memory _name,
+        string memory _image,
+        string memory _description, 
+        string memory _location, 
+        uint _price
+    ) public {
+        uint _sold = 0;
+        products[productsLength] = Product(
+            payable(msg.sender),
+            _name,
+            _image,
+            _description,
+            _location,
+            _price,
+            _sold
+        );
+        productsLength++;
+    }
+
+    function readProduct(uint _index) public view returns (
+        address payable,
+        string memory, 
+        string memory, 
+        string memory, 
+        string memory, 
+        uint, 
+        uint
+    ) {
+        return (
+            products[_index].owner,
+            products[_index].name, 
+            products[_index].image, 
+            products[_index].description, 
+            products[_index].location, 
+            products[_index].price,
+            products[_index].sold
+        );
+    }
+
+    function buyProduct(uint _index) public payable  {
+        require(
+          IERC20Token(cUsdTokenAddress).transferFrom(
+            msg.sender,
+            products[_index].owner,
+            products[_index].price
+          ),
+          "Transfer failed."
+        );
+        products[_index].sold++;
+    }
+
+    function editProduct(uint _index, 
+        string memory _name,
+        string memory _image,
+        string memory _description, 
+        string memory _location, 
+        uint _price
+        ) public {
+        require(products[_index].owner == msg.sender, "You can not edit this product.");
+        products[_index].name = _name;
+        products[_index].image = _image;
+        products[_index].description = _description;
+        products[_index].location = _location;
+        products[_index].price = _price;
+    }
+
+    function deleteProduct(uint _index) public {
+        require(products[_index].owner == msg.sender, "You can not delete this product.");
+        delete products[_index];
+    }
+
+    function getProductsLength() public view returns (uint) {
+        return (productsLength);
+    }
+}