How can I evaluate a chooser in C++ and get it to output a struct and an array of animation assets ??

Development Programming & Scripting
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1

Screenshot 2025-03-27 214020
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I want to do this in C++.
I think I need to use this function in ChooserFunctionLibrary.h :

UFUNCTION(BlueprintCallable, meta = (BlueprintThreadSafe, BlueprintInternalUseOnly = “true”, DeterminesOutputType = “ObjectClass”))
static TArray<UObject*> EvaluateObjectChooserBaseMulti(UPARAM(Ref) FChooserEvaluationContext& Context,UPARAM(Ref) const FInstancedStruct& ObjectChooser, TSubclassOf ObjectClass, bool bResultIsClass = false);

but I am not able to figure out how. So, I guess I am asking for an example of how to use this function.
Or maybe there is another way of doing it. Either way, please help. Thanks.

2

Hi!

As an example, you can check out this:

void YourCustomEvaluateChooser(UChooserTable* Chooser, const FYourInputData& _InputData, FYourOutputData& _OutputData)
{
    if (!IsValid(Chooser)) return;

    const FInstancedStruct ResultInstances = UChooserFunctionLibrary::MakeEvaluateChooser(Chooser);
    FChooserEvaluationContext EvaluationContext;
    
    FInstancedStruct InputStruct;
    InputStruct.InitializeAs<FYourInputData>();
    FYourInputData& InputData = InputStruct.GetMutable<FYourInputData>();
    InputData = _InputData;
    EvaluationContext.Params.Add(InputStruct);
    
    FInstancedStruct OutputStruct;
    OutputStruct.InitializeAs<FYourOutputData>();
    FYourOutputData& OutputData = OutputStruct.GetMutable<FYourOutputData>();
    EvaluationContext.Params.Add(OutputStruct);
    
    TArray<UObject*> EvaluateObjects = UChooserFunctionLibrary::EvaluateObjectChooserBaseMulti(
        EvaluationContext,
        ResultInstances,
        UAnimMontage::StaticClass()
    );

    TArray<UAnimSequence*> Sequences;
    for (UObject* Object : EvaluateObjects)
    {
        if (UAnimSequence* Sequence = Cast<UAnimSequence>(Object))
        {
            Sequences.Add(Sequence);
        }
    }

    _OutputData = OutputData;
}
1 Like
3

Thank you for your help. I will test this. Thank you again

4

The code compiled but now I can’t open the animation blueprint anymore it just crashes

5

There is a function, that is doing exactly what this “Evaluate Chooser” node does:

/**
   * Evaluate a chooser table and return the list of all selected UObjects
   *
   * @param ContextObject         (in) An Object from which the parameters to the Chooser Table will be read
   * @param ChooserTable          (in) The ChooserTable asset
   * @param ObjectClass       (in) Expected type of result objects
   */
   UFUNCTION(BlueprintPure, meta = (BlueprintThreadSafe, BlueprintInternalUseOnly = "true", DeterminesOutputType = "ObjectClass"))
   static UE_API TArray<UObject*> EvaluateChooserMulti(const UObject* ContextObject, const UChooserTable* ChooserTable, TSubclassOf<UObject> ObjectClass);

It’s in UChooserFunctionLibrary class. To use it, you need to include “ChooserFunctionLibrary.h” and add “Chooser” module in your *.Build.cs file.

1 Like
6

This is the correct answer, but man, the file is a mess, and the way you add parameters is so confusing.