Anatomia inteligentnych kontraktów

1// Przykład Solidity
2contract SimpleStorage {
3    uint storedData; // Zmienna stanu
4    // ...
5}
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1# Przykład Vyper
2storedData: int128
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1// Przykład Solidity
2function update_name(string value) public {
3    dapp_name = value;
4}
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1// Przykład 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// Przykład Solidity
2// Inicjuje dane umowy, ustawia `właściciela`
3// na adres twórcy kontraktu.
4constructor() public {
5    // Wszystkie inteligentne kontrakty opierają się na transakcjach zewnętrznych, aby wyzwolić swoje funkcje.
6    // `msg` to zmienna globalna zawierająca odpowiednie dane dotyczące danej transakcji,
7    // takie jak adres nadawcy i wartość ETH zawarta w transakcji.
8    // Dowiedz się więcej: 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# Przykład 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
5
6    // Called when the contract is deployed and initializes the value
7    constructor() public {
8        dapp_name = "My Example dapp";
9    }
10
11    // Get Function
12    function read_name() public view returns(string) {
13        return dapp_name;
14    }
15
16    // Set Function
17    function update_name(string value) public {
18        dapp_name = value;
19    }
20}
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1// Określa wersję Solidity przy użyciu wersji semantycznej.
2// Więcej informacji: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#pragma
3pragma solidity ^0.5.10;
4
5// Definiuje kontrakt o nazwie `HelloWorld`.
6// Kontrakt jest zbiorem funkcji i danych (jego stanu).
7// Po wdrożeniu kontrakt znajduje się pod określonym adresem w blockchainie Ethereum.
8// Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html
9contract HelloWorld {
10
11    // Deklaruje zmienną stanu `message` typu `string`.
12    // zmienne stanu to zmienne, których wartości są stale przechowywane w pamięci kontraktów.
13    // Słowo kluczowe `public` udostępnia zmienne spoza kontraktu
14    // i tworzy funkcję, którą inne kontrakty lub klienci mogą wywołać, aby uzyskać dostęp do tej wartości.
15    ciąg wiadomości publicznych;
16
17    // Podobne do wielu języków obiektowych opartych na klasie, konstruktorem jest
18    // specjalna funkcja, która jest wykonywana tylko w momencie tworzenia kontraktu.
19    // Konstruktory są używane do inicjowania danych kontraktu.
20    // Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constructors
21    constructor(string memory initMessage) public {
22        //Akceptuje argument ciągu `initMessage` i ustawia wartość
23        // na zmienną pamięci kontraktu `message`).
24        wiadomość = initMessage;
25    }
26
27    // funkcja publiczna, która akceptuje argument ciągu
28    // i aktualizuje zmienną pamięci `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    // Adres porównywalny z adresem e-mail - jest używany do indentyfikacji konta w Ethereum.
5    // Adresy mogą reprezentować inteligentne kontrakty lub konta zewnętrzne (użytkowników).
6    // Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/types.html#address
7    address public owner;
8
9    // Mapowanie jest zasadniczo strukturą danych o postaci tablicy skrótów.
10    // To mapowanie przypisuje niepodpisaną liczbę całkowitą (saldo tokena) do adresu (posiadacza tokenu).
11    // Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/types.html#mapping-types
12    mapowanie (adres => uint) publiczne saldo;
13
14    // Wydarzenia pozwalają na rejestrowanie aktywności w blockchain.
15    // Klienci Ethereum mogą słuchać zdarzeń, aby reagować na zmiany stanu kontraktu.
16    // Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/contracty. tml#events
17    Transferu zdarzeń (adres od, adres do kwoty uint);
18
19    // inicjuje dane umowy, ustawienie `właściciela`
20    // na adres twórcy kontraktu.
21    constructor() public {
22    // Wszystkie inteligentne kontrakty opierają się na transakcjach zewnętrznych, aby wyzwolić swoje funkcje.
23        // `msg` to zmienna globalna zawierająca odpowiednie dane dotyczące danej transakcji,
24    // takie jak adres nadawcy i wartość ETH zawarta w transakcji.
25        // Dowiedz się więcej: https://solidity.readthedocs.io/en/v0.5.10/units-and-global-variables.html#block-and-transaction-properties
26        owner = msg.sender;
27    }
28
29    // Tworzy liczbę nowych tokenów i wysyła je na adres.
30    function mint(address receiver, uint amount) public {
31        // `require` jest strukturą kontroli używaną do wymuszania pewnych warunków.
32        // Jeśli wyrażenie `require` oceni na `false`, wyzwalany jest wyjątek,
33        // który cofa wszystkie zmiany w stanie podczas bieżącego wywołąnia.
34        // Więcej informacji: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions
35
36        // Tylko właściciel kontraktu może wywołać tę funkcję
37        require(msg.sender == owner, "You are not the owner.");
38
39        // Wymusza maksymalną kwotę tokenów
40        require(amount < 1e60, "Maximum issuance exceeded");
41
42        // Zwiększa saldo `receiver` o `amount`
43        balances[receiver] += amount;
44    }
45
46    // Wysyła kwotę istniejących tokenów od dowolnego wywołującego na adres.
47    function transfer(address receiver, uint amount) public {
48        // Nadawca musi mieć wystarczającą ilość tokenów, aby wysłać
49        require(amount <= balances[msg.sender], "Insufficient balance.");
50
51        // Dostosowuje salda tokenów z dwóch adresów
52        balances[msg.sender] -= amount;
53        balances[receiver] += amount;
54
55        // Emituje wydarzenie zdefiniowane wcześniej
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.
4// In this case, a series of helper contracts from OpenZeppelin.
5
6
7// Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#importing-other-source-files
8
9import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721.sol";
10import "../node_modules/@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
11import "../node_modules/@openzeppelin/contracts/introspection/ERC165.sol";
12import "../node_modules/@openzeppelin/contracts/math/SafeMath.sol";
13
14// The `is` keyword is used to inherit functions and keywords from external contracts.
15// In this case, `CryptoPizza` inherits from the `IERC721` and `ERC165` contracts.
16
17
18// Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#inheritance
19contract CryptoPizza is IERC721, ERC165 {
20    // Uses OpenZeppelin's SafeMath library to perform arithmetic operations safely.
21    // Learn more: https://docs.openzeppelin.com/contracts/2.x/api/math#SafeMath
22    using SafeMath for uint256;
23
24    // Constant state variables in Solidity are similar to other languages
25    // but you must assign from an expression which is constant at compile time.
26
27
28    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constant-state-variables
29    uint256 constant dnaDigits = 10;
30    uint256 constant dnaModulus = 10 ** dnaDigits;
31    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;
32
33    // Struct types let you define your own type
34    // Learn more: https://solidity.readthedocs.io/en/v0.5.10/types.html#structs
35    struct Pizza {
36        string name;
37        uint256 dna;
38    }
39
40    // Creates an empty array of Pizza structs
41    Pizza[] public pizzas;
42
43    // Mapping from pizza ID to its owner's address
44    mapping(uint256 => address) public pizzaToOwner;
45
46    // Mapping from owner's address to number of owned token
47    mapping(address => uint256) public ownerPizzaCount;
48
49    // Mapping from token ID to approved address
50    mapping(uint256 => address) pizzaApprovals;
51
52    // You can nest mappings, this example maps owner to operator approvals
53    mapping(address => mapping(address => bool)) private operatorApprovals;
54
55    // Internal function to create a random Pizza from string (name) and DNA
56    function _createPizza(string memory _name, uint256 _dna)
57        // The `internal` keyword means this function is only visible
58        // within this contract and contracts that derive this contract
59        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#visibility-and-getters
60        internal
61        // `isUnique` is a function modifier that checks if the pizza already exists
62        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html#function-modifiers
63        isUnique(_name, _dna)
64    {
65        // Adds Pizza to array of Pizzas and get id
66        uint256 id = SafeMath.sub(pizzas.push(Pizza(_name, _dna)), 1);
67
68        // Checks that Pizza owner is the same as current user
69        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/control-structures.html#error-handling-assert-require-revert-and-exceptions
70        assert(pizzaToOwner[id] == address(0));
71
72        // Maps the Pizza to the owner
73        pizzaToOwner[id] = msg.sender;
74        ownerPizzaCount[msg.sender] = SafeMath.add(
75            ownerPizzaCount[msg.sender],
76            1
77        );
78    }
79
80    // Creates a random Pizza from string (name)
81    function createRandomPizza(string memory _name) public {
82        uint256 randDna = generateRandomDna(_name, msg.sender);
83        _createPizza(_name, randDna);
84    }
85
86    // Generates random DNA from string (name) and address of the owner (creator)
87    function generateRandomDna(string memory _str, address _owner)
88        public
89        // Functions marked as `pure` promise not to read from or modify the state
90        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#pure-functions
91        pure
92        returns (uint256)
93    {
94        // Generates random uint from string (name) + address (owner)
95        uint256 rand = uint256(keccak256(abi.encodePacked(_str))) +
96            uint256(_owner);
97        rand = rand % dnaModulus;
98        return rand;
99    }
100
101    // Returns array of Pizzas found by owner
102    function getPizzasByOwner(address _owner)
103        public
104        // Functions marked as `view` promise not to modify state
105        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/contracts.html#view-functions
106        view
107        returns (uint256[] memory)
108    {
109        // Uses the `memory` storage location to store values only for the
110        // lifecycle of this function call.
111        // Learn more: https://solidity.readthedocs.io/en/v0.5.10/introduction-to-smart-contracts.html#storage-memory-and-the-stack
112        uint256[] memory result = new uint256[](ownerPizzaCount[_owner]);
113        uint256 counter = 0;
114        for (uint256 i = 0; i < pizzas.length; i++) {
115            if (pizzaToOwner[i] == _owner) {
116                result[counter] = i;
117                counter++;
118            }
119        }
120        return result;
121    }
122
123    // Transfers Pizza and ownership to other address
124    function transferFrom(address _from, address _to, uint256 _pizzaId) public {
125        require(_from != address(0) && _to != address(0), "Invalid address.");
126        require(_exists(_pizzaId), "Pizza does not exist.");
127        require(_from != _to, "Cannot transfer to the same address.");
128        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
129
130        ownerPizzaCount[_to] = SafeMath.add(ownerPizzaCount[_to], 1);
131        ownerPizzaCount[_from] = SafeMath.sub(ownerPizzaCount[_from], 1);
132        pizzaToOwner[_pizzaId] = _to;
133
134        // Emits event defined in the imported IERC721 contract
135        emit Transfer(_from, _to, _pizzaId);
136        _clearApproval(_to, _pizzaId);
137    }
138
139    /**
140     * Safely transfers the ownership of a given token ID to another address
141     * If the target address is a contract, it must implement `onERC721Received`,
142     * which is called upon a safe transfer, and return the magic value
143     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
144     * otherwise, the transfer is reverted.
145    */
146    function safeTransferFrom(address from, address to, uint256 pizzaId)
147        public
148    {
149        // solium-disable-next-line arg-overflow
150        this.safeTransferFrom(from, to, pizzaId, "");
151    }
152
153    /**
154     * Safely transfers the ownership of a given token ID to another address
155     * If the target address is a contract, it must implement `onERC721Received`,
156     * which is called upon a safe transfer, and return the magic value
157     * `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`;
158     * otherwise, the transfer is reverted.
159     */
160    function safeTransferFrom(
161        address from,
162        address to,
163        uint256 pizzaId,
164        bytes memory _data
165    ) public {
166        this.transferFrom(from, to, pizzaId);
167        require(_checkOnERC721Received(from, to, pizzaId, _data), "Must implmement onERC721Received.");
168    }
169
170    /**
171     * Internal function to invoke `onERC721Received` on a target address
172     * The call is not executed if the target address is not a contract
173     */
174    function _checkOnERC721Received(
175        address from,
176        address to,
177        uint256 pizzaId,
178        bytes memory _data
179    ) internal returns (bool) {
180        if (!isContract(to)) {
181            return true;
182        }
183
184        bytes4 retval = IERC721Receiver(to).onERC721Received(
185            msg.sender,
186            from,
187            pizzaId,
188            _data
189        );
190        return (retval == _ERC721_RECEIVED);
191    }
192
193    // Burns a Pizza - destroys Token completely
194    // The `external` function modifier means this function is
195    // part of the contract interface and other contracts can call it
196    function burn(uint256 _pizzaId) external {
197        require(msg.sender != address(0), "Invalid address.");
198        require(_exists(_pizzaId), "Pizza does not exist.");
199        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
200
201        ownerPizzaCount[msg.sender] = SafeMath.sub(
202            ownerPizzaCount[msg.sender],
203            1
204        );
205        pizzaToOwner[_pizzaId] = address(0);
206    }
207
208    // Returns count of Pizzas by address
209    function balanceOf(address _owner) public view returns (uint256 _balance) {
210        return ownerPizzaCount[_owner];
211    }
212
213    // Returns owner of the Pizza found by id
214    function ownerOf(uint256 _pizzaId) public view returns (address _owner) {
215        address owner = pizzaToOwner[_pizzaId];
216        require(owner != address(0), "Invalid Pizza ID.");
217        return owner;
218    }
219
220    // Approves other address to transfer ownership of Pizza
221    function approve(address _to, uint256 _pizzaId) public {
222        require(msg.sender == pizzaToOwner[_pizzaId], "Must be the Pizza owner.");
223        pizzaApprovals[_pizzaId] = _to;
224        emit Approval(msg.sender, _to, _pizzaId);
225    }
226
227    // Returns approved address for specific Pizza
228    function getApproved(uint256 _pizzaId)
229        public
230        view
231        returns (address operator)
232    {
233        require(_exists(_pizzaId), "Pizza does not exist.");
234        return pizzaApprovals[_pizzaId];
235    }
236
237    /**
238     * Private function to clear current approval of a given token ID
239     * Reverts if the given address is not indeed the owner of the token
240     */
241    function _clearApproval(address owner, uint256 _pizzaId) private {
242        require(pizzaToOwner[_pizzaId] == owner, "Must be pizza owner.");
243        require(_exists(_pizzaId), "Pizza does not exist.");
244        if (pizzaApprovals[_pizzaId] != address(0)) {
245            pizzaApprovals[_pizzaId] = address(0);
246        }
247    }
248
249    /*
250     * Sets or unsets the approval of a given operator
251     * An operator is allowed to transfer all tokens of the sender on their behalf
252     */
253    function setApprovalForAll(address to, bool approved) public {
254        require(to != msg.sender, "Cannot approve own address");
255        operatorApprovals[msg.sender][to] = approved;
256        emit ApprovalForAll(msg.sender, to, approved);
257    }
258
259    // Tells whether an operator is approved by a given owner
260    function isApprovedForAll(address owner, address operator)
261        public
262        view
263        returns (bool)
264    {
265        return operatorApprovals[owner][operator];
266    }
267
268    // Takes ownership of Pizza - only for approved users
269    function takeOwnership(uint256 _pizzaId) public {
270        require(_isApprovedOrOwner(msg.sender, _pizzaId), "Address is not approved.");
271        address owner = this.ownerOf(_pizzaId);
272        this.transferFrom(owner, msg.sender, _pizzaId);
273    }
274
275    // Checks if Pizza exists
276    function _exists(uint256 pizzaId) internal view returns (bool) {
277        address owner = pizzaToOwner[pizzaId];
278        return owner != address(0);
279    }
280
281    // Checks if address is owner or is approved to transfer Pizza
282    function _isApprovedOrOwner(address spender, uint256 pizzaId)
283        internal
284        view
285        returns (bool)
286    {
287        address owner = pizzaToOwner[pizzaId];
288        // Disable solium check because of
289        // https://github.com/duaraghav8/Solium/issues/175
290        // solium-disable-next-line operator-whitespace
291        return (spender == owner ||
292            this.getApproved(pizzaId) == spender ||
293            this.isApprovedForAll(owner, spender));
294    }
295
296    // Check if Pizza is unique and doesn't exist yet
297    modifier isUnique(string memory _name, uint256 _dna) {
298        bool result = true;
299        for (uint256 i = 0; i < pizzas.length; i++) {
300            if (
301                keccak256(abi.encodePacked(pizzas[i].name)) ==
302                keccak256(abi.encodePacked(_name)) &&
303                pizzas[i].dna == _dna
304            ) {
305                result = false;
306            }
307        }
308        require(result, "Pizza with such name already exists.");
309        _;
310    }
311
312    // Returns whether the target address is a contract
313    function isContract(address account) internal view returns (bool) {
314        uint256 size;
315        // Currently there is no better way to check if there is a contract in an address
316        // than to check the size of the code at that address.
317        // See https://ethereum.stackexchange.com/a/14016/36603
318        // for more details about how this works.
319        // TODO Check this again before the Serenity release, because all addresses will be
320        // contracts then.
321
322
323        // solium-disable-next-line security/no-inline-assembly
324        assembly {
325            size := extcodesize(account)
326        }
327        return size > 0;
328    }
329}
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