UPARAM Specifiers - nullstar/SecondBrain GitHub Wiki

UPARAM Specifiers

UCLASS Specifiers | UFUNCTION Specifiers | UPROPERTY Specifiers | USTRUCT Specifiers

UPARAM(DisplayName="abc")

Allows renaming parameters in UFUNCTION functions.

UFUNCTION(BlueprintCallable)
void MakeDog(
  UPARAM(DisplayName = "Years (dog years)") float Years,
  UPARAM(DisplayName = "Fur Color") FLinearColor Color);
UPARAM(ref)

If a UFUNCTION parameter is a non-const reference, it is displayed as an output pin by default. It's assumed that the struct will be filled.

I would think hard about what the purpose is of your function when choosing if you need to use UPARAM(). Looking at the example code below:

  • FillDogInfo takes an empty data structure that is provided to it, and fills it out. In Blueprints it is shown as an output pin.
  • UseAndFillDogInfo takes a reference to a data structure as input. That means it can change the values within the data structure. If you do not need to change the values of the data structure, then see UseDogInfo.
  • UseDogInfo takes a const reference data structure. It cannot change the values of the data.
// Fill an empty data structure
UFUNCTION(BlueprintCallable)
void FillDogInfo(FDogInfo& OutResult);

// Use existing data, add some more
UFUNCTION(BlueprintCallable)
void UseAndFillDogInfo(
    UPARAM(ref) FDogInfo& SearchParams);

// Just use existing data and don't change it
UFUNCTION(BlueprintCallable)
void UseDogInfo(const FDogInfo& SearchParams);
UPARAM(meta=(AllowAbstract=true))

Works exclusively with TSubclassOf. By default, TSubclassOf<T> will allow abstract choosing classes.

UFUNCTION(BlueprintCallable, Category = "Composure", meta = (DeterminesOutputType = "OutputType"))
UCompositingElementOutput* FindOutputPass(UPARAM(meta = (AllowAbstract = "false"))TSubclassOf<UCompositingElementOutput> OutputType, FName OptionalPassName = NAME_None);
UPARAM(meta=(Categories))

Limits the Gameplay Tags that are selectable on the UFUNCTION. Works in the same way as the UPROPERTY Categories meta flag.

UFUNCTION(BlueprintCallable)
void SellItems(UPARAM(meta=(Categories="Inventory.Item"))FGameplayTag Itemtag, int32 Count);

UFUNCTION(BlueprintCallable, BlueprintAuthorityOnly, Category = GameplayEffects)
virtual void UpdateActiveGameplayEffectSetByCallerMagnitude(FActiveGameplayEffectHandle ActiveHandle, UPARAM(meta=(Categories = "SetByCaller"))FGameplayTag SetByCallerTag, float NewValue);

#Unreal #Specifiers

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