diff options
Diffstat (limited to 'docs/contracts.rst')
| -rw-r--r-- | docs/contracts.rst | 150 |
1 files changed, 82 insertions, 68 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index ca4e79c0..a0a3009b 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -40,7 +40,7 @@ This means that cyclic creation dependencies are impossible. :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.16; contract OwnedToken { // TokenCreator is a contract type that is defined below. @@ -52,7 +52,7 @@ This means that cyclic creation dependencies are impossible. // This is the constructor which registers the // creator and the assigned name. - function OwnedToken(bytes32 _name) { + function OwnedToken(bytes32 _name) public { // State variables are accessed via their name // and not via e.g. this.owner. This also applies // to functions and especially in the constructors, @@ -67,7 +67,7 @@ This means that cyclic creation dependencies are impossible. name = _name; } - function changeName(bytes32 newName) { + function changeName(bytes32 newName) public { // Only the creator can alter the name -- // the comparison is possible since contracts // are implicitly convertible to addresses. @@ -75,7 +75,7 @@ This means that cyclic creation dependencies are impossible. name = newName; } - function transfer(address newOwner) { + function transfer(address newOwner) public { // Only the current owner can transfer the token. if (msg.sender != owner) return; // We also want to ask the creator if the transfer @@ -90,6 +90,7 @@ This means that cyclic creation dependencies are impossible. contract TokenCreator { function createToken(bytes32 name) + public returns (OwnedToken tokenAddress) { // Create a new Token contract and return its address. @@ -99,16 +100,17 @@ This means that cyclic creation dependencies are impossible. return new OwnedToken(name); } - function changeName(OwnedToken tokenAddress, bytes32 name) { + function changeName(OwnedToken tokenAddress, bytes32 name) public { // Again, the external type of "tokenAddress" is // simply "address". tokenAddress.changeName(name); } - function isTokenTransferOK( - address currentOwner, - address newOwner - ) returns (bool ok) { + function isTokenTransferOK(address currentOwner, address newOwner) + public + view + returns (bool ok) + { // Check some arbitrary condition. address tokenAddress = msg.sender; return (keccak256(newOwner) & 0xff) == (bytes20(tokenAddress) & 0xff); @@ -171,10 +173,10 @@ return parameter list for functions. :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.16; contract C { - function f(uint a) private returns (uint b) { return a + 1; } + function f(uint a) private pure returns (uint b) { return a + 1; } function setData(uint a) internal { data = a; } uint public data; } @@ -193,13 +195,13 @@ In the following example, ``D``, can call ``c.getData()`` to retrieve the value uint private data; function f(uint a) private returns(uint b) { return a + 1; } - function setData(uint a) { data = a; } + function setData(uint a) public { data = a; } function getData() public returns(uint) { return data; } function compute(uint a, uint b) internal returns (uint) { return a+b; } } contract D { - function readData() { + function readData() public { C c = new C(); uint local = c.f(7); // error: member "f" is not visible c.setData(3); @@ -209,7 +211,7 @@ In the following example, ``D``, can call ``c.getData()`` to retrieve the value } contract E is C { - function g() { + function g() public { C c = new C(); uint val = compute(3, 5); // access to internal member (from derived to parent contract) } @@ -238,7 +240,7 @@ be done at declaration. contract Caller { C c = new C(); - function f() { + function f() public { uint local = c.data(); } } @@ -254,7 +256,7 @@ it is evaluated as a state variable. If it is accessed externally contract C { uint public data; - function x() { + function x() public { data = 3; // internal access uint val = this.data(); // external access } @@ -277,7 +279,7 @@ The next example is a bit more complex: It will generate a function of the following form:: - function data(uint arg1, bool arg2, uint arg3) returns (uint a, bytes3 b) { + function data(uint arg1, bool arg2, uint arg3) public returns (uint a, bytes3 b) { a = data[arg1][arg2][arg3].a; b = data[arg1][arg2][arg3].b; } @@ -302,7 +304,7 @@ inheritable properties of contracts and may be overridden by derived contracts. pragma solidity ^0.4.11; contract owned { - function owned() { owner = msg.sender; } + function owned() public { owner = msg.sender; } address owner; // This contract only defines a modifier but does not use @@ -323,7 +325,7 @@ inheritable properties of contracts and may be overridden by derived contracts. // "owned" and applies it to the "close"-function, which // causes that calls to "close" only have an effect if // they are made by the stored owner. - function close() onlyOwner { + function close() public onlyOwner { selfdestruct(owner); } } @@ -341,16 +343,16 @@ inheritable properties of contracts and may be overridden by derived contracts. mapping (address => bool) registeredAddresses; uint price; - function Register(uint initialPrice) { price = initialPrice; } + function Register(uint initialPrice) public { price = initialPrice; } // It is important to also provide the // "payable" keyword here, otherwise the function will // automatically reject all Ether sent to it. - function register() payable costs(price) { + function register() public payable costs(price) { registeredAddresses[msg.sender] = true; } - function changePrice(uint _price) onlyOwner { + function changePrice(uint _price) public onlyOwner { price = _price; } } @@ -368,7 +370,7 @@ inheritable properties of contracts and may be overridden by derived contracts. /// reentrant calls from within msg.sender.call cannot call f again. /// The `return 7` statement assigns 7 to the return value but still /// executes the statement `locked = false` in the modifier. - function f() noReentrancy returns (uint) { + function f() public noReentrancy returns (uint) { require(msg.sender.call()); return 7; } @@ -459,7 +461,7 @@ The following statements are considered modifying the state: pragma solidity ^0.4.16; contract C { - function f(uint a, uint b) view returns (uint) { + function f(uint a, uint b) public view returns (uint) { return a * (b + 42) + now; } } @@ -495,7 +497,7 @@ In addition to the list of state modifying statements explained above, the follo pragma solidity ^0.4.16; contract C { - function f(uint a, uint b) pure returns (uint) { + function f(uint a, uint b) public pure returns (uint) { return a * (b + 42); } } @@ -561,7 +563,7 @@ Please ensure you test your fallback function thoroughly to ensure the execution // Sending Ether to this contract will cause an exception, // because the fallback function does not have the "payable" // modifier. - function() { x = 1; } + function() public { x = 1; } uint x; } @@ -569,11 +571,11 @@ Please ensure you test your fallback function thoroughly to ensure the execution // This contract keeps all Ether sent to it with no way // to get it back. contract Sink { - function() payable { } + function() public payable { } } contract Caller { - function callTest(Test test) { + function callTest(Test test) public { test.call(0xabcdef01); // hash does not exist // results in test.x becoming == 1. @@ -597,7 +599,7 @@ This also applies to inherited functions. The following example shows overloadin ``f`` function in the scope of contract ``A``. :: - + pragma solidity ^0.4.16; contract A { @@ -721,7 +723,7 @@ All non-indexed arguments will be stored in the data part of the log. uint _value ); - function deposit(bytes32 _id) payable { + function deposit(bytes32 _id) public payable { // Any call to this function (even deeply nested) can // be detected from the JavaScript API by filtering // for `Deposit` to be called. @@ -770,7 +772,7 @@ as topics. The event call above can be performed in the same way as pragma solidity ^0.4.10; contract C { - function f() { + function f() public payable { bytes32 _id = 0x420042; log3( bytes32(msg.value), @@ -814,7 +816,7 @@ Details are given in the following example. :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.16; contract owned { function owned() { owner = msg.sender; } @@ -836,12 +838,12 @@ Details are given in the following example. // without body. If a contract does not implement all // functions it can only be used as an interface. contract Config { - function lookup(uint id) returns (address adr); + function lookup(uint id) public returns (address adr); } contract NameReg { - function register(bytes32 name); - function unregister(); + function register(bytes32 name) public; + function unregister() public; } // Multiple inheritance is possible. Note that "owned" is @@ -849,7 +851,7 @@ Details are given in the following example. // instance of "owned" (as for virtual inheritance in C++). contract named is owned, mortal { function named(bytes32 name) { - Config config = Config(0xd5f9d8d94886e70b06e474c3fb14fd43e2f23970); + Config config = Config(0xD5f9D8D94886E70b06E474c3fB14Fd43E2f23970); NameReg(config.lookup(1)).register(name); } @@ -858,9 +860,9 @@ Details are given in the following example. // types of output parameters, that causes an error. // Both local and message-based function calls take these overrides // into account. - function kill() { + function kill() public { if (msg.sender == owner) { - Config config = Config(0xd5f9d8d94886e70b06e474c3fb14fd43e2f23970); + Config config = Config(0xD5f9D8D94886E70b06E474c3fB14Fd43E2f23970); NameReg(config.lookup(1)).unregister(); // It is still possible to call a specific // overridden function. @@ -873,11 +875,11 @@ Details are given in the following example. // provided in the header (or modifier-invocation-style at // the constructor of the derived contract (see below)). contract PriceFeed is owned, mortal, named("GoldFeed") { - function updateInfo(uint newInfo) { + function updateInfo(uint newInfo) public { if (msg.sender == owner) info = newInfo; } - function get() constant returns(uint r) { return info; } + function get() public view returns(uint r) { return info; } uint info; } @@ -889,22 +891,22 @@ seen in the following example:: pragma solidity ^0.4.0; contract owned { - function owned() { owner = msg.sender; } + function owned() public { owner = msg.sender; } address owner; } contract mortal is owned { - function kill() { + function kill() public { if (msg.sender == owner) selfdestruct(owner); } } contract Base1 is mortal { - function kill() { /* do cleanup 1 */ mortal.kill(); } + function kill() public { /* do cleanup 1 */ mortal.kill(); } } contract Base2 is mortal { - function kill() { /* do cleanup 2 */ mortal.kill(); } + function kill() public { /* do cleanup 2 */ mortal.kill(); } } contract Final is Base1, Base2 { @@ -918,23 +920,23 @@ derived override, but this function will bypass pragma solidity ^0.4.0; contract owned { - function owned() { owner = msg.sender; } + function owned() public { owner = msg.sender; } address owner; } contract mortal is owned { - function kill() { + function kill() public { if (msg.sender == owner) selfdestruct(owner); } } contract Base1 is mortal { - function kill() { /* do cleanup 1 */ super.kill(); } + function kill() public { /* do cleanup 1 */ super.kill(); } } contract Base2 is mortal { - function kill() { /* do cleanup 2 */ super.kill(); } + function kill() public { /* do cleanup 2 */ super.kill(); } } contract Final is Base2, Base1 { @@ -963,11 +965,11 @@ the base constructors. This can be done in two ways:: contract Base { uint x; - function Base(uint _x) { x = _x; } + function Base(uint _x) public { x = _x; } } contract Derived is Base(7) { - function Derived(uint _y) Base(_y * _y) { + function Derived(uint _y) Base(_y * _y) public { } } @@ -1032,7 +1034,7 @@ Contract functions can lack an implementation as in the following example (note pragma solidity ^0.4.0; contract Feline { - function utterance() returns (bytes32); + function utterance() public returns (bytes32); } Such contracts cannot be compiled (even if they contain @@ -1042,11 +1044,11 @@ but they can be used as base contracts:: pragma solidity ^0.4.0; contract Feline { - function utterance() returns (bytes32); + function utterance() public returns (bytes32); } contract Cat is Feline { - function utterance() returns (bytes32) { return "miaow"; } + function utterance() public returns (bytes32) { return "miaow"; } } If a contract inherits from an abstract contract and does not implement all non-implemented functions by overriding, it will itself be abstract. @@ -1077,7 +1079,7 @@ Interfaces are denoted by their own keyword: pragma solidity ^0.4.11; interface Token { - function transfer(address recipient, uint amount); + function transfer(address recipient, uint amount) public; } Contracts can inherit interfaces as they would inherit other contracts. @@ -1120,7 +1122,7 @@ more advanced example to implement a set). :: - pragma solidity ^0.4.11; + pragma solidity ^0.4.16; library Set { // We define a new struct datatype that will be used to @@ -1134,6 +1136,7 @@ more advanced example to implement a set). // to call the first parameter 'self', if the function can // be seen as a method of that object. function insert(Data storage self, uint value) + public returns (bool) { if (self.flags[value]) @@ -1143,6 +1146,7 @@ more advanced example to implement a set). } function remove(Data storage self, uint value) + public returns (bool) { if (!self.flags[value]) @@ -1152,6 +1156,8 @@ more advanced example to implement a set). } function contains(Data storage self, uint value) + public + view returns (bool) { return self.flags[value]; @@ -1161,7 +1167,7 @@ more advanced example to implement a set). contract C { Set.Data knownValues; - function register(uint value) { + function register(uint value) public { // The library functions can be called without a // specific instance of the library, since the // "instance" will be the current contract. @@ -1190,19 +1196,19 @@ custom types without the overhead of external function calls: :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.16; library BigInt { struct bigint { uint[] limbs; } - function fromUint(uint x) internal returns (bigint r) { + function fromUint(uint x) internal pure returns (bigint r) { r.limbs = new uint[](1); r.limbs[0] = x; } - function add(bigint _a, bigint _b) internal returns (bigint r) { + function add(bigint _a, bigint _b) internal pure returns (bigint r) { r.limbs = new uint[](max(_a.limbs.length, _b.limbs.length)); uint carry = 0; for (uint i = 0; i < r.limbs.length; ++i) { @@ -1224,11 +1230,11 @@ custom types without the overhead of external function calls: } } - function limb(bigint _a, uint _limb) internal returns (uint) { + function limb(bigint _a, uint _limb) internal pure returns (uint) { return _limb < _a.limbs.length ? _a.limbs[_limb] : 0; } - function max(uint a, uint b) private returns (uint) { + function max(uint a, uint b) private pure returns (uint) { return a > b ? a : b; } } @@ -1236,7 +1242,7 @@ custom types without the overhead of external function calls: contract C { using BigInt for BigInt.bigint; - function f() { + function f() public pure { var x = BigInt.fromUint(7); var y = BigInt.fromUint(uint(-1)); var z = x.add(y); @@ -1294,13 +1300,14 @@ available without having to add further code. Let us rewrite the set example from the :ref:`libraries` in this way:: - pragma solidity ^0.4.11; + pragma solidity ^0.4.16; // This is the same code as before, just without comments library Set { struct Data { mapping(uint => bool) flags; } function insert(Data storage self, uint value) + public returns (bool) { if (self.flags[value]) @@ -1310,6 +1317,7 @@ Let us rewrite the set example from the } function remove(Data storage self, uint value) + public returns (bool) { if (!self.flags[value]) @@ -1319,6 +1327,8 @@ Let us rewrite the set example from the } function contains(Data storage self, uint value) + public + view returns (bool) { return self.flags[value]; @@ -1329,7 +1339,7 @@ Let us rewrite the set example from the using Set for Set.Data; // this is the crucial change Set.Data knownValues; - function register(uint value) { + function register(uint value) public { // Here, all variables of type Set.Data have // corresponding member functions. // The following function call is identical to @@ -1340,10 +1350,14 @@ Let us rewrite the set example from the It is also possible to extend elementary types in that way:: - pragma solidity ^0.4.0; + pragma solidity ^0.4.16; library Search { - function indexOf(uint[] storage self, uint value) returns (uint) { + function indexOf(uint[] storage self, uint value) + public + view + returns (uint) + { for (uint i = 0; i < self.length; i++) if (self[i] == value) return i; return uint(-1); @@ -1354,11 +1368,11 @@ It is also possible to extend elementary types in that way:: using Search for uint[]; uint[] data; - function append(uint value) { + function append(uint value) public { data.push(value); } - function replace(uint _old, uint _new) { + function replace(uint _old, uint _new) public { // This performs the library function call uint index = data.indexOf(_old); if (index == uint(-1)) |