Return From Interface Function Returning Null

Development Programming & Scripting UI
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1

I am attempting to work with the UE4 Interfaces in C++ and, it seems like this should all work, I get no errors or compiler issues but I am getting results that make no sense. This is a very simple interface that should return a component from a character.

  #include "CoreMinimal.h"
    #include "UObject/ObjectMacros.h"
    #include "UObject/Interface.h"
    #include "InventoryInterface.generated.h"
    
    class UInventoryComponent;
    class AEquipmentItem;
    
    // This class does not need to be modified.
    UINTERFACE(BlueprintType)
    class UInventoryInterface : public UInterface
    {
    	GENERATED_BODY()
    };
    
    /**
     * 
     */
    class SWORDSNMAGICANDSTUFF_API IInventoryInterface
    {
    	GENERATED_BODY()
    
    public:
    	UFUNCTION(BlueprintCallable, BlueprintIMplementableEvent, Category = "Inventory")
    	UInventoryComponent* GetInventoryComponent();
    };

and then in the .h file for my character…

class SWORDSNMAGICANDSTUFF_API ASNMCombatCharacter : public ASNMCharacter, public IAbilitySystemInterface, public IInventoryInterface
{
	GENERATED_BODY()
		
public:
UFUNCTION(BlueprintImplementableEvent, BlueprintCallable, Category="Inventory")
    		UInventoryComponent* GetInventoryComponent();
    		virtual UInventoryComponent* GetInventoryComponent_Implementation();

and the .cpp

UInventoryComponent* ASNMCombatCharacter::GetInventoryComponent_Implementation()
{
	return InventoryComponent;
}

Yet this always returns null, I am positive the class has the component which is stored in that variable.

This is where it is created in the parent class.

InventoryComponent = CreateDefaultSubobject<UInventoryComponent>(TEXT("Player Inventory"));

I have tried several methods to pull this info through the interface and they all return null.

2

Further testing shows it doesnt seem to actually be calling the function on the character class. Documentaion on Interfaces in C++ seem to be pretty contradictory to reality. When attempting to add override to this which is show in EVERY doc it fails to compile.

3

In your implementation, you don’t have to re-state the UFUNCTION macro nor the original getter… but you must do the _Implementation, like you have done.
However, one thing you’re missing is the override specifier at the end of your function declaration.

Perhaps something like:

class SWORDSNMAGICANDSTUFF_API ASNMCombatCharacter : public ASNMCharacter, public IAbilitySystemInterface, public IInventoryInterface
 {
     GENERATED_BODY()
         
 public:
     virtual UInventoryComponent* GetInventoryComponent_Implementation() override;

I dropped the UFUNCTION and the getter, then added the override specifier at the end.

Good luck!

4

ill give this a try!

5

Part of the problem was a typo in the original code so it was not implementing the interface UFUNCTION properly, but outside of that this answer was correct, and provides a cleaner implementation with less funk.