UnrealScript

UnrealScript (often abbreviated to UScript) is the scripting language of the Unreal Engine and is used for authoring game code and gameplay events. The language was designed for simple, high-level game programming.^[1] The UnrealScript interpreter was programmed by Tim Sweeney, who also created an earlier game scripting language, ZZT-oop.

Similar to Java, UnrealScript is object-oriented without multiple inheritance (classes all inherit from a common Object class), and classes are defined in individual files named for the class they define. Unlike Java, UnrealScript is case-insensitive, and does not have object wrappers for primitive types. Interfaces are only supported in Unreal Engine generation 3 and a few Unreal Engine 2 games. UnrealScript supports operator overloading, but not method overloading, except for optional parameters.

By making the process of modifying the game easier, UnrealScript helped enable the growth of a large modding community around Unreal. This greatly added to the overall longevity of Unreal and provided an incentive for new development.

Syntax

Code comments

Unreal X-Editor showing syntax highlight using one of the in-built color scheme.

// Single-line comment
class Foo extends Object;
 
/* Multi-line
   comment */
var Object Foo;

Data types

Primitive types

• Bool - A boolean that allows the values true, and false, which is the same as 1, and 0
• Byte - A 8Bit Unsigned integer value that may range from 0 to 255
• Enum
• Float
• Int - A 32Bit integer value that may range from -2147483648 to 2147483647
• Name - A more restricted version of String, only allowing the following characters ([a-zA-Z0-9_\- ]*) as expressed in regex. e.g. 'name_example'
• String - A series of Unicode characters such as "A B C"

Reference types

• Class
• Delegate
• Interface
• Object
• Pointer

Composite types

• Array
• Struct

Functions

UnrealScript uses functions similar to C/C++/Java. Functions are declared by the keyword: function, followed by an optional return type, its required name, and finally its function parameters.

The declaration of a function can look like this:

[modifiers] function [[modifiers] datatype] name( [parameters] ) [const]; the semicolon is only necessary if the function has no body.

An example of a very simple additive function in UnrealScript:

function int Add( int a, int b )
{
    return a + b;
}

"Hello, world" example

The following is a hello world example using the syntax of UnrealScript.^[2]

class HelloWorld extends GameInfo;
 
event InitGame( string Options, out string Error )
{
    `log( "Hello, world!" );
}

The following text will be printed to the output console when HelloWorld is initializing:

Hello, world!

See also

References

External links

• UnrealScript Language Reference for UE2
• UnrealScript Language Reference for UE3
• UnrealScript Language Reference circa 1998 (Original Unreal)
• UnrealWiki: UnrealScript