Constants - Revision history

Eliot at 00:50, 19 April 2010

2010-04-19T00:50:09Z

Eliot: Correct the keyword and moved the text above navbox...

2010-04-19T00:21:31Z

Correct the keyword and moved the text above navbox...

UnrealJoe: /* Usage */

2010-04-18T21:14:53Z

‎Usage

Eliot: /* Declaration */

2010-04-15T22:21:16Z

‎Declaration

Wormbo: Created page with 'UnrealScript constants are basically alias names for specific literals. ==Declaration== Constants can be declared almost anywhere in a class. Usually they are defined at the...'

2009-06-14T11:37:19Z

Created page with 'UnrealScript constants are basically alias names for specific literals. ==Declaration== Constants can be declared almost anywhere in a class. Usually they are defined at the...'

New page

UnrealScript constants are basically alias names for specific [[literals]].

==Declaration==
Constants can be declared almost anywhere in a class. Usually they are defined at the top of the class, right after the class declaration or between variable declarations, but they can also appear in the body of a state or function declaration. The syntax is really simple:
'''const''' ''constantname'' '''=''' ''value''''';'''
While this looks similar to a variable assignment, the value in a constant declaration must be a single [[literal]] without any function calls or operators. The pseudo-function <code>[[ArrayCount]]'''('''''variablename''''')'''</code> is also allowed, as it is evaluated at compile-time, and is translated to the number of elements in the specified static array variable. [[Enum]] values are not supported, this includes the ''EnumCount'' and ''_MAX'' enum properties.

Unlike [[Variables#Access modifiers|constant variables]], constants are really "constant" and will never change at runtime. The '''const''' modifier in variable declarations really only prevents the variable to be used on the left side of an assignment or as '''out''' parameter in a function call. [[Native code]] can still assign to '''const''' variables, and in fact that modifier is used for many variables with native side effects that must be changed through corresponding native [[wp:accessor|accessor]] functions.

==Usage==
Constants can be used almost in every place where a literal can be used. Integer constants are even allowed as the size of [[static arrays]]. The only exceptions are the [[defaultproperties]] block, where constants are only allowed starting with [[Unreal Engine 3]], and other constant definitions. For some reason constants don't count as "constant" there.

When the compiler encounters a constant name in code, and that place allows the use of literals, the constant name is replaced by the literal assigned in the constant definition.

{{navbox unrealscript}}

@@ Line 13: / Line 13: @@
 When the compiler encounters a constant name in code, and that place allows the use of literals, the constant name is replaced by the literal assigned in the constant definition.
-Starting with [[Unreal Engine 3]] you can access constants from other classes by using the const keyword like shown below
+Starting with [[Unreal Engine 3]] you can access constants from other classes by using the const keyword like shown below.
-<uscript>class MyConstsClass extends object;
+<uscript>class ClassA extends Object;
-const LuckyNumber = 7;
+const ConstA = "UnrealWiki";
 </uscript>
 <uscript>
-class ExampleClass extends object;
+class ClassB extends Object;
-protected final function ExampleFunction()
+final protected function string GetConstA()
+{
-     local int MyInteger;
+     return class'ClassA'.const.ConstA;
-−
-    MyInteger = MyConstsClass.const.LuckyNumber;
+}
 </uscript>
 {{navbox unrealscript}}

@@ Line 13: / Line 13: @@
 When the compiler encounters a constant name in code, and that place allows the use of literals, the constant name is replaced by the literal assigned in the constant definition.
-{{navbox unrealscript}}
+Starting with [[Unreal Engine 3]] you can access constants from other classes by using the const keyword like shown below
 <uscript>class MyConstsClass extends object;
@@ Line 27: / Line 26: @@
      local int MyInteger;
-     MyInteger = MyConstsClass.static.LuckyNumber;
+     MyInteger = MyConstsClass.const.LuckyNumber;
+}
 </uscript>

← Older revision		Revision as of 21:14, 18 April 2010
Line 14:		Line 14:

	{{navbox unrealscript}}		{{navbox unrealscript}}
		+
		+	Constants can be accessed between script classes by using the static keyword,
		+	<uscript>class MyConstsClass extends object;
		+
		+	const LuckyNumber = 7;
		+	</uscript>
		+	<uscript>
		+	class ExampleClass extends object;
		+
		+	protected final function ExampleFunction()
		+	{
		+	local int MyInteger;
		+
		+	MyInteger = MyConstsClass.static.LuckyNumber;
		+	}
		+	</uscript>

@@ Line 2: / Line 2: @@
 ==Declaration==
-Constants can be declared almost anywhere in a class. Usually they are defined at the top of the class, right after the class declaration or between variable declarations, but they can also appear in the body of a state or function declaration. The syntax is really simple:
+Constants can be declared almost anywhere in a class. Usually they are defined at the top of the class, right after the class declaration or between variable declarations, but they can also appear in the body of structs, states and function declarations. The syntax is really simple:
   '''const''' ''constantname'' '''=''' ''value''''';'''
 While this looks similar to a variable assignment, the value in a constant declaration must be a single [[literal]] without any function calls or operators. The pseudo-function <code>[[ArrayCount]]'''('''''variablename''''')'''</code> is also allowed, as it is evaluated at compile-time, and is translated to the number of elements in the specified static array variable. [[Enum]] values are not supported, this includes the ''EnumCount'' and ''_MAX'' enum properties.