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Diffstat (limited to 'docs/contracts.rst')
| -rw-r--r-- | docs/contracts.rst | 50 |
1 files changed, 32 insertions, 18 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index edc42c3d..9145f016 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -145,11 +145,11 @@ This means that cyclic creation dependencies are impossible. .. index:: ! visibility, external, public, private, internal -.. _visibility-and-accessors: +.. _visibility-and-getters: -************************ -Visibility and Accessors -************************ +********************** +Visibility and Getters +********************** Since Solidity knows two kinds of function calls (internal ones that do not create an actual EVM call (also called @@ -173,7 +173,7 @@ and the default is ``internal``. ``public``: Public functions are part of the contract interface and can be either called internally or via - messages. For public state variables, an automatic accessor + messages. For public state variables, an automatic getter function (see below) is generated. ``internal``: @@ -243,12 +243,12 @@ In the following example, ``D``, can call ``c.getData()`` to retrieve the value } } -.. index:: ! accessor;function, ! function;accessor +.. index:: ! getter;function, ! function;getter -Accessor Functions -================== +Getter Functions +================ -The compiler automatically creates accessor functions for +The compiler automatically creates getter functions for all **public** state variables. For the contract given below, the compiler will generate a function called ``data`` that does not take any arguments and returns a ``uint``, the value of the state @@ -271,7 +271,7 @@ be done at declaration. } } -The accessor functions have external visibility. If the +The getter functions have external visibility. If the symbol is accessed internally (i.e. without ``this.``), it is evaluated as a state variable and if it is accessed externally (i.e. with ``this.``), it is evaluated as a function. @@ -428,8 +428,25 @@ change by overriding). Constant State Variables ************************ -State variables can be declared as constant (this is not yet implemented -for array and struct types and not possible for mapping types). +State variables can be declared as ``constant``. In this case, they have to be +assigned from an expression which is a constant at compile time. Any expression +that accesses storage, blockchain data (e.g. ``now``, ``this.balance`` or +``block.number``) or +execution data (``msg.gas``) or make calls to external contracts are disallowed. Expressions +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). + +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. +This feature is not yet fully usable. + +The compiler does not reserve a storage slot for these variables and every occurrence is +replaced by the respective constant expression (which might be computed to a single value by the optimizer). + +Not all types for constants are implemented at this time. The only supported types are +value types and strings. :: @@ -438,12 +455,9 @@ for array and struct types and not possible for mapping types). contract C { uint constant x = 32**22 + 8; string constant text = "abc"; + bytes32 constant myHash = keccak256("abc"); } -This has the effect that the compiler does not reserve a storage slot -for these variables and every occurrence is replaced by their constant value. - -The value expression can only contain integer arithmetics. ****************** Constant Functions @@ -462,7 +476,7 @@ Functions can be declared constant. These functions promise not to modify the st } .. note:: - Accessor methods are marked constant. + Getter methods are marked constant. .. warning:: The compiler does not enforce yet that a constant method is not modifying state. @@ -882,7 +896,7 @@ Inheriting Different Kinds of Members of the Same Name When the inheritance results in a contract with a function and a modifier of the same name, it is considered as an error. This error is produced also by an event and a modifier of the same name, and a function and an event of the same name. -As an exception, a state variable accessor can override a public function. +As an exception, a state variable getter can override a public function. .. index:: ! contract;abstract, ! abstract contract |