Function Libraries

Interacting with unreal from scripts often happens through function libraries. These are exposed to script as namespaces containing a set of related functions.

For example, to set a timer you can call System::SetTimer():

class ATimerExample : AActor
{
    UFUNCTION(BlueprintOverride)
    void BeginPlay()
    {
        // Execute this.OnTimerExecuted() after 2 seconds
        System::SetTimer(this, n"OnTimerExecuted", 2.0, bLooping = false);
    }

    UFUNCTION()
    private void OnTimerExecuted()
    {
        Print("Timer executed!");
    }
}

Common Libraries

Clicking the library will bring you to the API documentation for them, listing the available functions:

• Math:: - All standard math functionality
• Gameplay:: - Game functionality such as streaming, damage, player handling
• System:: - Engine functionality such as timers, traces, debug rendering
• Niagara:: - Spawning and controlling particle systems
• Widget:: - UMG widget functionality

Namespace Simplification

The functions for function libraries in script are automatically taken from blueprint function library classes in C++.

Before binding, the angelscript plugin simplifies the name of the class to make a shorter namespace. For example, the functions in the System:: namespace are automatically sourced from the UKismetSystemLibrary class in C++.

Common prefixes and suffixes that get stripped automatically are:

• U…Statics
• U…Library
• U…FunctionLibrary
• UKismet…Library
• UKismet…FunctionLibrary
• UBlueprint…Library
• UBlueprint…FunctionLibrary

For some examples of how namespaces are simplified:

• UNiagaraFunctionLibrary becomes Niagara::
• UWidgetBlueprintLibrary becomes Widget::
• UKismetSystemLibrary becomes System::
• UGameplayStatics becomes Gameplay::

Math Library

Because blueprint and C++ have fairly different ways of doing math code, we have decided to keep the Math:: namespace in script closer to the C++ FMath:: namespace in general.

Sticking closer to C++ math eases the transition for experienced programmers and lets code be ported between the two more easily.

This means that UKismetMathLibrary gets ignored for automatic binding.