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Diffstat (limited to 'docs/contracts.rst')
| -rw-r--r-- | docs/contracts.rst | 54 |
1 files changed, 40 insertions, 14 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index 9145f016..8d7af2c1 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -27,7 +27,7 @@ From ``web3.js``, i.e. the JavaScript API, this is done as follows:: // Need to specify some source including contract name for the data param below - var source = "contract CONTRACT_NAME { function CONTRACT_NAME(unit a, uint b) {} }"; + var source = "contract CONTRACT_NAME { function CONTRACT_NAME(uint a, uint b) {} }"; // The json abi array generated by the compiler var abiArray = [ @@ -327,7 +327,7 @@ inheritable properties of contracts and may be overridden by derived contracts. :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.11; contract owned { function owned() { owner = msg.sender; } @@ -341,8 +341,7 @@ inheritable properties of contracts and may be overridden by derived contracts. // function is executed and otherwise, an exception is // thrown. modifier onlyOwner { - if (msg.sender != owner) - throw; + require(msg.sender == owner); _; } } @@ -390,7 +389,7 @@ inheritable properties of contracts and may be overridden by derived contracts. contract Mutex { bool locked; modifier noReentrancy() { - if (locked) throw; + require(!locked); locked = true; _; locked = false; @@ -401,7 +400,7 @@ inheritable properties of contracts and may be overridden by derived contracts. /// 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) { - if (!msg.sender.call()) throw; + require(msg.sender.call()); return 7; } } @@ -436,7 +435,7 @@ execution data (``msg.gas``) or make calls to external contracts are disallowed. that might have a side-effect on memory allocation are allowed, but those that might have a side-effect on other memory objects are not. The built-in functions ``keccak256``, ``sha256``, ``ripemd160``, ``ecrecover``, ``addmod`` and ``mulmod`` -are allowed (ever though they do call external contracts). +are allowed (even though they do call external contracts). The reason behind allowing side-effects on the memory allocator is that it should be possible to construct complex objects like e.g. lookup-tables. @@ -922,6 +921,35 @@ Such contracts cannot be compiled (even if they contain implemented functions al If a contract inherits from an abstract contract and does not implement all non-implemented functions by overriding, it will itself be abstract. +.. index:: ! contract;interface, ! interface contract + +********** +Interfaces +********** + +Interfaces are similar to abstract contracts, but they cannot have any functions implemented. There are further restrictions: + +#. Cannot inherit other contracts or interfaces. +#. Cannot define constructor. +#. Cannot define variables. +#. Cannot define structs. +#. Cannot define enums. + +Some of these restrictions might be lifted in the future. + +Interfaces are basically limited to what the Contract ABI can represent and the conversion between the ABI and +an Interface should be possible without any information loss. + +Interfaces are denoted by their own keyword: + +:: + + interface Token { + function transfer(address recipient, uint amount); + } + +Contracts can inherit interfaces as they would inherit other contracts. + .. index:: ! library, callcode, delegatecall .. _libraries: @@ -960,7 +988,7 @@ more advanced example to implement a set). :: - pragma solidity ^0.4.0; + pragma solidity ^0.4.11; library Set { // We define a new struct datatype that will be used to @@ -1006,8 +1034,7 @@ more advanced example to implement a set). // The library functions can be called without a // specific instance of the library, since the // "instance" will be the current contract. - if (!Set.insert(knownValues, value)) - throw; + require(Set.insert(knownValues, value)); } // In this contract, we can also directly access knownValues.flags, if we want. } @@ -1101,7 +1128,7 @@ Restrictions for libraries in comparison to contracts: - No state variables - Cannot inherit nor be inherited -- Cannot recieve Ether +- Cannot receive Ether (These might be lifted at a later point.) @@ -1137,7 +1164,7 @@ available without having to add further code. Let us rewrite the set example from the :ref:`libraries` in this way:: - pragma solidity ^0.4.0; + pragma solidity ^0.4.11; // This is the same code as before, just without comments library Set { @@ -1178,8 +1205,7 @@ Let us rewrite the set example from the // corresponding member functions. // The following function call is identical to // Set.insert(knownValues, value) - if (!knownValues.insert(value)) - throw; + require(knownValues.insert(value)); } } |