Anatomi kontrak pintar

1// Solidity example // Contoh Solidity
2contract SimpleStorage {
3    uint storedData; // State variable // Variabel state
4    // ... // ...
5}
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1# Vyper example # Contoh Vyper
2storedData: int128
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1// Solidity example // Contoh Solidity
2function update_name(string value) public {
3    dapp_name = value;
4}
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1// Solidity example // Contoh Solidity
2function balanceOf(address _owner) public view returns (uint256 _balance) {
3    return ownerPizzaCount[_owner];
4}
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1dappName: public(string)
2
3@view
4@public
5def readName() -> string:
6  return dappName
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1// Solidity example // Contoh Solidity
2// Initializes the contract's data, setting the `owner` // Menginisialisasi data kontrak, mengatur `owner`
3// to the address of the contract creator. // ke alamat pembuat kontrak.
4constructor() public {
5    // All smart contracts rely on external transactions to trigger its functions. // Semua kontrak pintar bergantung pada transaksi eksternal untuk memicu fungsinya.
6    // `msg` is a global variable that includes relevant data on the given transaction, // `msg` adalah variabel global yang mencakup data relevan pada transaksi yang diberikan,
7    // such as the address of the sender and the ETH value included in the transaction. // seperti alamat pengirim dan nilai ETH yang disertakan dalam transaksi.
8    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/units-and-global-variables.html#block-and-transaction-properties // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/units-and-global-variables.html#block-and-transaction-properties
9    owner = msg.sender;
10}
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1# Vyper example # Contoh Vyper
2
3@external
4def __init__(_beneficiary: address, _bidding_time: uint256):
5    self.beneficiary = _beneficiary
6    self.auctionStart = block.timestamp
7    self.auctionEnd = self.auctionStart + _bidding_time
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1pragma solidity >=0.4.0 <=0.6.0;
2
3contract ExampleDapp {
4    string dapp_name; // state variable // variabel state
5
6    // Called when the contract is deployed and initializes the value // Dipanggil saat kontrak disebarkan dan menginisialisasi nilai
7    constructor() public {
8        dapp_name = "My Example dapp";
9    }
10
11    // Get Function // Fungsi Get
12    function read_name() public view returns(string) {
13        return dapp_name;
14    }
15
16    // Set Function // Fungsi Set
17    function update_name(string value) public {
18        dapp_name = value;
19    }
20}
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1// Specifies the version of Solidity, using semantic versioning. // Menentukan versi Solidity, menggunakan pembuatan versi semantik.
2// Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#pragma // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#pragma
3pragma solidity ^0.5.10;
4
5// Defines a contract named `HelloWorld`. // Mendefinisikan kontrak bernama `HelloWorld`.
6// A contract is a collection of functions and data (its state). // Kontrak adalah kumpulan fungsi dan data (state-nya).
7// Once deployed, a contract resides at a specific address on the Ethereum blockchain. // Setelah disebarkan, kontrak berada di alamat tertentu di blockchain Ethereum.
8// Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html
9contract HelloWorld {
10
11    // Declares a state variable `message` of type `string`. // Mendeklarasikan variabel state `message` dengan tipe `string`.
12    // State variables are variables whose values are permanently stored in contract storage. // Variabel state adalah variabel yang nilainya disimpan secara permanen di penyimpanan kontrak.
13    // The keyword `public` makes variables accessible from outside a contract // Kata kunci `public` membuat variabel dapat diakses dari luar kontrak
14    // and creates a function that other contracts or clients can call to access the value. // dan membuat fungsi yang dapat dipanggil oleh kontrak atau klien lain untuk mengakses nilainya.
15    string public message;
16
17    // Similar to many class-based object-oriented languages, a constructor is // Mirip dengan banyak bahasa berorientasi objek berbasis kelas, konstruktor adalah
18    // a special function that is only executed upon contract creation. // fungsi khusus yang hanya dieksekusi saat pembuatan kontrak.
19    // Constructors are used to initialize the contract's data. // Konstruktor digunakan untuk menginisialisasi data kontrak.
20    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constructors // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constructors
21    constructor(string memory initMessage) public {
22        // Accepts a string argument `initMessage` and sets the value // Menerima argumen string `initMessage` dan mengatur nilainya
23        // into the contract's `message` storage variable). // ke dalam variabel penyimpanan `message` kontrak).
24        message = initMessage;
25    }
26
27    // A public function that accepts a string argument // Fungsi publik yang menerima argumen string
28    // and updates the `message` storage variable. // dan memperbarui variabel penyimpanan `message`.
29    function update(string memory newMessage) public {
30        message = newMessage;
31    }
32}
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1pragma solidity ^0.5.10;
2
3contract Token {
4    // An `address` is comparable to an email address - it's used to identify an account on Ethereum. // Sebuah `address` sebanding dengan alamat email - ini digunakan untuk mengidentifikasi akun di Ethereum.
5    // Addresses can represent a smart contract or an external (user) accounts. // Alamat dapat mewakili kontrak pintar atau akun (pengguna) eksternal.
6    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/types.html#address // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/types.html#address
7    address public owner;
8
9    // A `mapping` is essentially a hash table data structure. // Sebuah `mapping` pada dasarnya adalah struktur data tabel hash.
10    // This `mapping` assigns an unsigned integer (the token balance) to an address (the token holder). // `mapping` ini menetapkan bilangan bulat tak bertanda (saldo token) ke sebuah alamat (pemegang token).
11    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/types.html#mapping-types // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/types.html#mapping-types
12    mapping (address => uint) public balances;
13
14    // Events allow for logging of activity on the blockchain. // Event memungkinkan pencatatan aktivitas di blockchain.
15    // Ethereum clients can listen for events in order to react to contract state changes. // Klien Ethereum dapat mendengarkan event untuk bereaksi terhadap perubahan state kontrak.
16    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#events // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#events
17    event Transfer(address from, address to, uint amount);
18
19    // Initializes the contract's data, setting the `owner` // Menginisialisasi data kontrak, mengatur `owner`
20    // to the address of the contract creator. // ke alamat pembuat kontrak.
21    constructor() public {
22        // All smart contracts rely on external transactions to trigger its functions. // Semua kontrak pintar bergantung pada transaksi eksternal untuk memicu fungsinya.
23        // `msg` is a global variable that includes relevant data on the given transaction, // `msg` adalah variabel global yang mencakup data relevan pada transaksi yang diberikan,
24        // such as the address of the sender and the ETH value included in the transaction. // seperti alamat pengirim dan nilai ETH yang disertakan dalam transaksi.
25        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/units-and-global-variables.html#block-and-transaction-properties // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/units-and-global-variables.html#block-and-transaction-properties
26        owner = msg.sender;
27    }
28
29    // Creates an amount of new tokens and sends them to an address. // Membuat sejumlah token baru dan mengirimkannya ke sebuah alamat.
30    function mint(address receiver, uint amount) public {
31        // `require` is a control structure used to enforce certain conditions. // `require` adalah struktur kontrol yang digunakan untuk memaksakan kondisi tertentu.
32        // If a `require` statement evaluates to `false`, an exception is triggered, // Jika pernyataan `require` dievaluasi menjadi `false`, pengecualian akan dipicu,
33        // which reverts all changes made to the state during the current call. // yang mengembalikan semua perubahan yang dibuat pada state selama panggilan saat ini.
34        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions
35
36        // Only the contract owner can call this function // Hanya pemilik kontrak yang dapat memanggil fungsi ini
37        require(msg.sender == owner, "You are not the owner.");
38
39        // Enforces a maximum amount of tokens // Memaksakan jumlah maksimum token
40        require(amount < 1e60, "Maximum issuance exceeded");
41
42        // Increases the balance of `receiver` by `amount` // Meningkatkan saldo `receiver` sebesar `amount`
43        balances[receiver] += amount;
44    }
45
46    // Sends an amount of existing tokens from any caller to an address. // Mengirim sejumlah token yang ada dari pemanggil mana pun ke sebuah alamat.
47    function transfer(address receiver, uint amount) public {
48        // The sender must have enough tokens to send // Pengirim harus memiliki cukup token untuk dikirim
49        require(amount <= balances[msg.sender], "Insufficient balance.");
50
51        // Adjusts token balances of the two addresses // Menyesuaikan saldo token dari kedua alamat
52        balances[msg.sender] -= amount;
53        balances[receiver] += amount;
54
55        // Emits the event defined earlier // Memancarkan event yang didefinisikan sebelumnya
56        emit Transfer(msg.sender, receiver, amount);
57    }
58}
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1pragma solidity ^0.5.10;
2
3// Imports symbols from other files into the current contract. // Mengimpor simbol dari file lain ke dalam kontrak saat ini.
4// In this case, a series of helper contracts from OpenZeppelin. // Dalam hal ini, serangkaian kontrak pembantu dari OpenZeppelin.
5// Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#importing-other-source-files // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#importing-other-source-files
6
7import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721.sol";
8import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
9import "../node_modules/@openzeppelin/contracts/introspection/ERC165.sol";
10import "../node_modules/@openzeppelin/contracts/math/SafeMath.sol";
11
12// The `is` keyword is used to inherit functions and keywords from external contracts. // Kata kunci `is` digunakan untuk mewarisi fungsi dan kata kunci dari kontrak eksternal.
13// In this case, `CryptoPizza` inherits from the `IERC721` and `ERC165` contracts. // Dalam hal ini, `CryptoPizza` mewarisi dari kontrak `IERC721` dan `ERC165`.
14// Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#inheritance // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#inheritance
15contract CryptoPizza is IERC721, ERC165 {
16    // Uses OpenZeppelin's SafeMath library to perform arithmetic operations safely. // Menggunakan pustaka SafeMath OpenZeppelin untuk melakukan operasi aritmatika dengan aman.
17    // Learn more: https://docs.openzeppelin.com/contracts/2.x/api/math#SafeMath // Pelajari lebih lanjut: https://docs.openzeppelin.com/contracts/2.x/api/math#SafeMath
18    using SafeMath for uint256;
19
20    // Constant state variables in Solidity are similar to other languages // Variabel state konstan di Solidity mirip dengan bahasa lain
21    // but you must assign from an expression which is constant at compile time. // tetapi Anda harus menetapkan dari ekspresi yang konstan pada waktu kompilasi.
22    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constant-state-variables // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constant-state-variables
23    uint256 constant dnaDigits = 10;
24    uint256 constant dnaModulus = 10 ** dnaDigits;
25    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;
26
27    // Struct types let you define your own type // Tipe struct memungkinkan Anda mendefinisikan tipe Anda sendiri
28    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/types.html#structs // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/types.html#structs
29    struct Pizza {
30        string name;
31        uint256 dna;
32    }
33
34    // Creates an empty array of Pizza structs // Membuat array kosong dari struct Pizza
35    Pizza[] public pizzas;
36
37    // Mapping from pizza ID to its owner's address // Pemetaan dari ID pizza ke alamat pemiliknya
38    mapping(uint256 => address) public pizzaToOwner;
39
40    // Mapping from owner's address to number of owned token // Pemetaan dari alamat pemilik ke jumlah token yang dimiliki
41    mapping(address => uint256) public ownerPizzaCount;
42
43    // Mapping from token ID to approved address // Pemetaan dari ID token ke alamat yang disetujui
44    mapping(uint256 => address) pizzaApprovals;
45
46    // You can nest mappings, this example maps owner to operator approvals // Anda dapat menyarangkan pemetaan, contoh ini memetakan pemilik ke persetujuan operator
47    mapping(address => mapping(address => bool)) private operatorApprovals;
48
49    // Internal function to create a random Pizza from string (name) and DNA // Fungsi internal untuk membuat Pizza acak dari string (nama) dan DNA
50    function _createPizza(string memory _name, uint256 _dna)
51        // The `internal` keyword means this function is only visible // Kata kunci `internal` berarti fungsi ini hanya terlihat
52        // within this contract and contracts that derive this contract // di dalam kontrak ini dan kontrak yang diturunkan dari kontrak ini
53        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#visibility-and-getters // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#visibility-and-getters
54        internal
55        // `isUnique` is a function modifier that checks if the pizza already exists // `isUnique` adalah pengubah fungsi yang memeriksa apakah pizza sudah ada
56        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html#function-modifiers // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html#function-modifiers
57        isUnique(_name, _dna)
58    {
59        // Adds Pizza to array of Pizzas and get id // Menambahkan Pizza ke array Pizza dan mendapatkan id
60        uint256 id = SafeMath.sub(pizzas.push(Pizza(_name, _dna)), 1);
61
62        // Checks that Pizza owner is the same as current user // Memeriksa bahwa pemilik Pizza sama dengan pengguna saat ini
63        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions
64
65        // note that address(0) is the zero address, // perhatikan bahwa address(0) adalah alamat nol,
66        // indicating that pizza[id] is not yet allocated to a particular user. // menunjukkan bahwa pizza[id] belum dialokasikan ke pengguna tertentu.
67
68        assert(pizzaToOwner[id] == address(0));
69
70        // Maps the Pizza to the owner // Memetakan Pizza ke pemilik
71        pizzaToOwner[id] = msg.sender;
72        ownerPizzaCount[msg.sender] = SafeMath.add(
73            ownerPizzaCount[msg.sender],
74            1
75        );
76    }
77
78    // Creates a random Pizza from string (name) // Membuat Pizza acak dari string (nama)
79    function createRandomPizza(string memory _name) public {
80        uint256 randDna = generateRandomDna(_name, msg.sender);
81        _createPizza(_name, randDna);
82    }
83
84    // Generates random DNA from string (name) and address of the owner (creator) // Menghasilkan DNA acak dari string (nama) dan alamat pemilik (pembuat)
85    function generateRandomDna(string memory _str, address _owner)
86        public
87        // Functions marked as `pure` promise not to read from or modify the state // Fungsi yang ditandai sebagai `pure` berjanji untuk tidak membaca dari atau memodifikasi state
88        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#pure-functions // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#pure-functions
89        pure
90        returns (uint256)
91    {
92        // Generates random uint from string (name) + address (owner) // Menghasilkan uint acak dari string (nama) + alamat (pemilik)
93        uint256 rand = uint256(keccak256(abi.encodePacked(_str))) +
94            uint256(_owner);
95        rand = rand % dnaModulus;
96        return rand;
97    }
98
99    // Returns array of Pizzas found by owner // Mengembalikan array Pizza yang ditemukan oleh pemilik
100    function getPizzasByOwner(address _owner)
101        public
102        // Functions marked as `view` promise not to modify state // Fungsi yang ditandai sebagai `view` berjanji untuk tidak memodifikasi state
103        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#view-functions // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#view-functions
104        view
105        returns (uint256[] memory)
106    {
107        // Uses the `memory` storage location to store values only for the // Menggunakan lokasi penyimpanan `memory` untuk menyimpan nilai hanya untuk
108        // lifecycle of this function call. // siklus hidup panggilan fungsi ini.
109        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/introduction-to-smart-contracts.html#storage-memory-and-the-stack // Pelajari lebih lanjut: https://solidity.readthedocs.io/en/v0.5.10/introduction-to-smart-contracts.html#storage-memory-and-the-stack
110        uint256[] memory result = new uint256[](ownerPizzaCount[_owner]);
111        uint256 counter = 0;
112        for (uint256 i = 0; i < pizzas.length; i++) {
113            if (pizzaToOwner[i] == _owner) {
114                result[counter] = i;
115                counter++;
116            }
117        }
118        return result;
119    }
120
121    // Transfers Pizza and ownership to other address // Mentransfer Pizza dan kepemilikan ke alamat lain
122    function transferFrom(address _from, address _to, uint256 _pizzaId) public {
123        require(_from != address(0) && _to != address(0), "Invalid address.");
124        require(_exists(_pizzaId), "Pizza does not exist.");
125        require(_from != _to, "Cannot transfer to the same address.");
126        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
127
128        ownerPizzaCount[_to] = SafeMath.add(ownerPizzaCount[_to], 1);
129        ownerPizzaCount[_from] = SafeMath.sub(ownerPizzaCount[_from], 1);
130        pizzaToOwner[_pizzaId] = _to;
131
132        // Emits event defined in the imported IERC721 contract // Memancarkan event yang didefinisikan dalam kontrak IERC721 yang diimpor
133        emit Transfer(_from, _to, _pizzaId);
134        _clearApproval(_to, _pizzaId);
135    }
136
137    /* *
138     * Mentransfer kepemilikan ID token yang diberikan dengan aman ke alamat lain
139     * Jika alamat target adalah kontrak, ia harus mengimplementasikan `onERC721Received`,
140     * yang dipanggil saat transfer aman, dan mengembalikan nilai ajaib
141     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
142     * jika tidak, transfer akan dikembalikan. */
143    /**
144     * Safely transfers the ownership of a given token ID to another address
145     * If the target address is a contract, it must implement `onERC721Received`,
146     * which is called upon a safe transfer, and return the magic value
147     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
148     * otherwise, the transfer is reverted.
149    */
150    function safeTransferFrom(address from, address to, uint256 pizzaId)
151        public
152    {
153        // solium-disable-next-line arg-overflow // solium-disable-next-line arg-overflow
154        this.safeTransferFrom(from, to, pizzaId, "");
155    }
156
157    /* *
158     * Mentransfer kepemilikan ID token yang diberikan dengan aman ke alamat lain
159     * Jika alamat target adalah kontrak, ia harus mengimplementasikan `onERC721Received`,
160     * yang dipanggil saat transfer aman, dan mengembalikan nilai ajaib
161     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
162     * jika tidak, transfer akan dikembalikan. */
163    /**
164     * Safely transfers the ownership of a given token ID to another address
165     * If the target address is a contract, it must implement `onERC721Received`,
166     * which is called upon a safe transfer, and return the magic value
167     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
168     * otherwise, the transfer is reverted.
169     */
170    function safeTransferFrom(
171        address from,
172        address to,
173        uint256 pizzaId,
174        bytes memory _data
175    ) public {
176        this.transferFrom(from, to, pizzaId);
177        require(_checkOnERC721Received(from, to, pizzaId, _data), "Must implement onERC721Received.");
178    }
179
180    /* *
181     * Fungsi internal untuk memanggil `onERC721Received` pada alamat target
182     * Panggilan tidak dieksekusi jika alamat target bukan kontrak */
183    /**
184     * Internal function to invoke `onERC721Received` on a target address
185     * The call is not executed if the target address is not a contract
186     */
187    function _checkOnERC721Received(
188        address from,
189        address to,
190        uint256 pizzaId,
191        bytes memory _data
192    ) internal returns (bool) {
193        if (!isContract(to)) {
194            return true;
195        }
196
197        bytes4 retval = IERC721Receiver(to).onERC721Received(
198            msg.sender,
199            from,
200            pizzaId,
201            _data
202        );
203        return (retval == _ERC721_RECEIVED);
204    }
205
206    // Burns a Pizza - destroys Token completely // Membakar Pizza - menghancurkan Token sepenuhnya
207    // The `external` function modifier means this function is // Pengubah fungsi `external` berarti fungsi ini adalah
208    // part of the contract interface and other contracts can call it // bagian dari antarmuka kontrak dan kontrak lain dapat memanggilnya
209    function burn(uint256 _pizzaId) external {
210        require(msg.sender != address(0), "Invalid address.");
211        require(_exists(_pizzaId), "Pizza does not exist.");
212        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
213
214        ownerPizzaCount[msg.sender] = SafeMath.sub(
215            ownerPizzaCount[msg.sender],
216            1
217        );
218        pizzaToOwner[_pizzaId] = address(0);
219    }
220
221    // Returns count of Pizzas by address // Mengembalikan jumlah Pizza berdasarkan alamat
222    function balanceOf(address _owner) public view returns (uint256 _balance) {
223        return ownerPizzaCount[_owner];
224    }
225
226    // Returns owner of the Pizza found by id // Mengembalikan pemilik Pizza yang ditemukan berdasarkan id
227    function ownerOf(uint256 _pizzaId) public view returns (address _owner) {
228        address owner = pizzaToOwner[_pizzaId];
229        require(owner != address(0), "Invalid Pizza ID.");
230        return owner;
231    }
232
233    // Approves other address to transfer ownership of Pizza // Menyetujui alamat lain untuk mentransfer kepemilikan Pizza
234    function approve(address _to, uint256 _pizzaId) public {
235        require(msg.sender == pizzaToOwner[_pizzaId], "Must be the Pizza owner.");
236        pizzaApprovals[_pizzaId] = _to;
237        emit Approval(msg.sender, _to, _pizzaId);
238    }
239
240    // Returns approved address for specific Pizza // Mengembalikan alamat yang disetujui untuk Pizza tertentu
241    function getApproved(uint256 _pizzaId)
242        public
243        view
244        returns (address operator)
245    {
246        require(_exists(_pizzaId), "Pizza does not exist.");
247        return pizzaApprovals[_pizzaId];
248    }
249
250    /* *
251     * Fungsi privat untuk menghapus persetujuan saat ini dari ID token yang diberikan
252     * Dikembalikan jika alamat yang diberikan memang bukan pemilik token */
253    /**
254     * Private function to clear current approval of a given token ID
255     * Reverts if the given address is not indeed the owner of the token
256     */
257    function _clearApproval(address owner, uint256 _pizzaId) private {
258        require(pizzaToOwner[_pizzaId] == owner, "Must be pizza owner.");
259        require(_exists(_pizzaId), "Pizza does not exist.");
260        if (pizzaApprovals[_pizzaId] != address(0)) {
261            pizzaApprovals[_pizzaId] = address(0);
262        }
263    }
264
265    /* * Mengatur atau membatalkan persetujuan dari operator yang diberikan
266     * Operator diizinkan untuk mentransfer semua token pengirim atas nama mereka */
267    /*
268     * Sets or unsets the approval of a given operator
269     * An operator is allowed to transfer all tokens of the sender on their behalf
270     */
271    function setApprovalForAll(address to, bool approved) public {
272        require(to != msg.sender, "Cannot approve own address");
273        operatorApprovals[msg.sender][to] = approved;
274        emit ApprovalForAll(msg.sender, to, approved);
275    }
276
277    // Tells whether an operator is approved by a given owner // Memberi tahu apakah operator disetujui oleh pemilik yang diberikan
278    function isApprovedForAll(address owner, address operator)
279        public
280        view
281        returns (bool)
282    {
283        return operatorApprovals[owner][operator];
284    }
285
286    // Takes ownership of Pizza - only for approved users // Mengambil kepemilikan Pizza - hanya untuk pengguna yang disetujui
287    function takeOwnership(uint256 _pizzaId) public {
288        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
289        address owner = this.ownerOf(_pizzaId);
290        this.transferFrom(owner, msg.sender, _pizzaId);
291    }
292
293    // Checks if Pizza exists // Memeriksa apakah Pizza ada
294    function _exists(uint256 pizzaId) internal view returns (bool) {
295        address owner = pizzaToOwner[pizzaId];
296        return owner != address(0);
297    }
298
299    // Checks if address is owner or is approved to transfer Pizza // Memeriksa apakah alamat adalah pemilik atau disetujui untuk mentransfer Pizza
300    function _isApprovedOrOwner(address spender, uint256 pizzaId)
301        internal
302        view
303        returns (bool)
304    {
305        address owner = pizzaToOwner[pizzaId];
306        // Disable solium check because of // Nonaktifkan pemeriksaan solium karena
307        // https://github.com/duaraghav8/Solium/issues/175 // https://github.com/duaraghav8/Solium/issues/175
308        // solium-disable-next-line operator-whitespace // solium-disable-next-line operator-whitespace
309        return (spender == owner ||
310            this.getApproved(pizzaId) == spender ||
311            this.isApprovedForAll(owner, spender));
312    }
313
314    // Check if Pizza is unique and doesn't exist yet // Periksa apakah Pizza unik dan belum ada
315    modifier isUnique(string memory _name, uint256 _dna) {
316        bool result = true;
317        for (uint256 i = 0; i < pizzas.length; i++) {
318            if (
319                keccak256(abi.encodePacked(pizzas[i].name)) ==
320                keccak256(abi.encodePacked(_name)) &&
321                pizzas[i].dna == _dna
322            ) {
323                result = false;
324            }
325        }
326        require(result, "Pizza with such name already exists.");
327        _;
328    }
329
330    // Returns whether the target address is a contract // Mengembalikan apakah alamat target adalah kontrak
331    function isContract(address account) internal view returns (bool) {
332        uint256 size;
333        // Currently there is no better way to check if there is a contract in an address // Saat ini tidak ada cara yang lebih baik untuk memeriksa apakah ada kontrak di sebuah alamat
334        // than to check the size of the code at that address. // daripada memeriksa ukuran kode di alamat tersebut.
335        // See https://ethereum.stackexchange.com/a/14016/36603 // Lihat https://ethereum.stackexchange.com/a/14016/36603
336        // for more details about how this works. // untuk detail lebih lanjut tentang cara kerjanya.
337        // TODO Check this again before the Serenity release, because all addresses will be // TODO Periksa ini lagi sebelum rilis Serenity, karena semua alamat akan menjadi
338        // contracts then. // kontrak pada saat itu.
339        // solium-disable-next-line security/no-inline-assembly // solium-disable-next-line security/no-inline-assembly
340        assembly {
341            size := extcodesize(account)
342        }
343        return size > 0;
344    }
345}
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