Make array input optional (UFUNCTION)

Jamendxman3 · November 18, 2015, 6:11pm

I have this UFUNCTION (Used as blueprint node):


UFUNCTION(BlueprintPure, meta = (FriendlyName = "Get My Stuff"), Category = "MyCategory")
		static void GetMyStuff(FMyStruct FilterData, TArray<TEnumAsByte<EMyEnum>> Filters, bool& ReturnValue);

I get compile errors when I don’t pass in an array, and I am wanting to make the underlined parameters be optional. I am currently doing this in order to work-around the problem:

Any ideas?

mid_gen · November 18, 2015, 6:36pm

You need to provide a default value (which could be null), and make it your last argument, or provide an overloaded version of the function that omits that argument.

Alderbit · November 18, 2015, 7:03pm

I’ve seen the AutoCreateRefTerm specifier used for the purpose of making array parameters optional. Documentation is pretty lacking but it appears to create an empty array if the pin is not hooked up. Your function declaration would change to


UFUNCTION(BlueprintPure, meta = (FriendlyName = "Get My Stuff", **AutoCreateRefTerm = "Filters"**), Category = "MyCategory")
static void GetMyStuff(FMyStruct FilterData, TArray<TEnumAsByte<EMyEnum>> Filters, bool& ReturnValue);

Edit: you should also probably change Filters to be a constant reference type if possible.

Jamendxman3 · November 18, 2015, 7:13pm

Alderbit;422305:

I’ve seen the AutoCreateRefTerm specifier used for the purpose of making array parameters optional. Documentation is pretty lacking but it appears to create an empty array if the pin is not hooked up. Your function declaration would change to
UFUNCTION(BlueprintPure, meta = (FriendlyName = "Get My Stuff", **AutoCreateRefTerm = "Filters"**), Category = "MyCategory")
static void GetMyStuff(FMyStruct FilterData, TArray<TEnumAsByte<EMyEnum>> Filters, bool& ReturnValue);

I am getting an instant crash when compiling the blueprint without the array pin connected now No minidump for the crash either.

Alderbit · November 18, 2015, 7:49pm

I’m unable to reproduce a crash in either 4.9 or 4.10. Which engine version are you using, and can you show how the enumeration used in the array is declared?

Jamendxman3 · November 18, 2015, 7:51pm

Lol, I was using 4.6. I upgraded to 4.10 and it is working fine now. Thanks for helping and taking the time to test for crashes though

Alderbit · November 18, 2015, 7:52pm

Haha, ok glad you got it working.

UnrealEverything · November 19, 2015, 8:51am

The idea is good but from my experience in practice doesn’t work as long as the function name is the same. If I remember correctly UnrealHeaderTool will complain about it and not even start compiling. Possibly because functions are mapped only by their name which would be ambiguous.