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| {{Stub}}
| | [[Category:Sandbox]] |
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| A '''variable''' is a "storage container" or "named placeholder" for data. You can read and modify the data once this container is created.
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| == Requirements ==
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| The following links guide to the basics to understand this article:
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| * [[ArmA: Introduction to Scripting]]
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| * [[Identifier]]
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| == Initialization ==
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| The first thing you have to do is to find a name for your variable. This name is called [[identifier]]. Read the article [[Identifier]] for more information.
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| Once you know a name, you have to tell the game engine that you are going to use this identifier. This is called '''initialization'''. Then you may do anything with this variable.
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| Don't worry: This sounds more dramatic than it is. You can initialize any variable by assigning a value to it.
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| myVariable = 0;
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| Querying undefined (or uninitialized) variables returns [[nil]] (undefined value). When converted to [[String|Strings]] with [[str]], they will always return [[scalar bool array string 0xe0ffffef]] (in [[Armed Assault]]) or [[scalar bool array string 0xfcffffef]] (in [[Operation Flashpoint]]).
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| myString = str(undefinedVar);
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| myString => "scalar bool array string 0xe0ffffef"
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| Thus you can't really apply any [[Operators|operations]] on variables before they are initialized with a start value.
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| == Deletion ==
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| Once created, variables will take up space in your computer memory. This is not drastic for small variables, but if you use a big number of very large variables, you should undefine any variables that are not needed anymore. This can be done with the command [[nil]].
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| hugeVariable = nil;
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| This effectively destroys a variable as if it had never existed.
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| == Namespace ==
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| Variables are only visible in certain areas (namespaces) of the game. This prevents name conflicts between different variables in different [[Script (File)|scripts]].
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| There are three namespaces:
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| ; local
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| : A variable is only visible in the [[Script (File)|script]] in which it was defined.
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| ; global
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| : A variable is visible on the whole computer where it is defined.
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| ; public
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| : A variable is broadcasted over the network and visible on all computers connected to the network.
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| === Local Variables ===
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| Local variables are only visible in a specific [[Script (File)|script]]. The whole code in this script has access to the variable, that includes also [[Function|functions]] called within the script.
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| The [[identifier]] of variables local to a [[Script (File)|script]] always has to start with an underscore.
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| _myLocalVariable = 0;
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| In functions you should additionally mark variables as local using the command [[private]]. Otherwise you may modify local variables of the calling script that are visible in the function.
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| private "_myLocalVariable";
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| _myLocalVariable = 0;
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| You may also pass more [[Identifier|identifiers]] to the private command using an [[Array]].
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| private ["_myLocalVariable1", "_myLocalVariable2", ...];
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| === Global Variables ===
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| Global variables are visible on the whole computer where they are defined. Names given to units in the [[Mission Editor]] are also global variables pointing to those units, which may not be redefined or modified.
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| [[Identifier]]s of global variables ''must not'' start with underscore. Otherwise there are the same rules as for all [[Identifier|identifiers]].
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| myGlobalVariable = 0;
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| === Public Variables ===
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| Public variables are global variables that are visible on all computers in the network. You can never have true public variables, but you can emulate their behaviour.
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| The value of a global variable gets broadcasted over the network using [[publicVariable]]. After the call of this command the variable will have the same value on all [[Client|clients]]. Once you modify the variable though you have to broadcast it manually ''again'' with [[publicVariable]].
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| == Scope ==
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| If a local variable is initialized within a [[Control Structures]] (i.e. [[if]], [[for]], [[switch]], [[while]]) its scope will stay ''within'' this structure (i.e. outside of the structure it will still be seen as undefined). This does not apply to global or public variables.
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| <code>if (alive player) then {_living=true}; hint format["%1",_living];</code>
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| Returns "scalar bool array string 0xe0ffffef", since the local variable was not initialized ''before'' being used within a control structure.
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| <code>_dead=true; if (alive player) then {_dead=false}; hint format["%1",_dead];
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| </code>
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| Returns "false", since the variable was initialized before the if...then.<br>
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| To initialize local variables, so that they are available throughout the whole script (including any control structures), either initialize it via the [[private]] command (e.g. ''private ["_varname"];''), or by assigning a default value to it (e.g. ''varname=0;'').
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| == Data Types ==
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| Variables may store certain values. The kind of the value specifies the ''type'' of the variable. Different [[Operators|operators]] and [[:Category:Scripting Commands|commands]] require variables to be of different types.
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| Read the article [[Data Types]] for more information about variable types.
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| == Multiplayer Considerations ==
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| FILL IN
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| == See also ==
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| * [[Data Types]]
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| [[Category: Scripting_Topics]] | |
