How does ConstructorHelpers::FClassFinder work?

Development Programming & Scripting C++
1

Hi there,

in my current project I need a way to in C++ either

a) find all classes inheriting from a certain C++ base class (including all Blueprint-generated classes) or
b) find a class by its name (again, including Blueprint-generatec classes)

I’ve tried a lot of things but couldn’t get anything to work in a standalone game (some things worked in the editor, but not in the game). Then today I came across this:

My problem is that I just have no idea how FClassFinder works and it’s impossible to find any kind of useful information about it on the internet. I’ve tried a few things myself, but so far I only got assertion fails. Can anyone give a usage example on this function? As in: what is the template parameter I have to pass in (I assume this is my C++ base-class?) and what kind of string do I have to pass in? And does this support both C++ and Blueprint-classes?

I’m on Unreal Engine 4.1.1, by the way. Don’t know if this is important, but it seems that the function’s implementation has changed since then.

Thanks in advance

2

You can iterate over all actors in the world and do a cast to your specific class:

3

That won’t work in my case because there aren’t any actors of the classes I’m searching for in the world at all.

4

Currently (AFAIK it was completely changed since 4.1.1) it works this way.

A code from ShooterGame sample:


static ConstructorHelpers::FClassFinder<APawn> BotPawnOb(TEXT("/Game/Blueprints/Pawns/BotPawn"));
BotPawnClass = BotPawnOb.Class;

where BotPawnClass is:


TSubclassOf<class APawn> BotPawnClass;

Notice, that the given path, does not include the exact class object (that would be “/Game/Blueprints/Pawns/BotPawn_C”), but only the blueprint asset.

2 Likes
5

Thanks, that actually seems quite helpful! By now I’ve solved my problem in another (less elegant) way, using FObjectFinder to load the UBlueprint I needed, but this should come in handy if I switch to another UE version in the future.

Another question, though: Is there a way to get a blueprint’s path at runtime? Assuming I had:


static ConstructorHelpers::FClassFinder<APawn> BotPawnOb(TEXT("/Game/Blueprints/Pawns/BotPawn"));
UBlueprintGeneratedClass* BotPawnClass = Cast<UBlueprintGeneratedClass>(BotPawnOb.Class);
UBlueprint* BotPawnBlueprint = Cast<UBlueprint>(BotPawnClass->ClassGeneratedBy);

Now I can easily get my blueprint’s name by doing


BotPawnBlueprint->GetName()->ToString();

which would return “BotPawn” in this case. But is there away to actually get the full path to my blueprint (“/Game/Blueprints/Pawns/BotPawn” in this case) from either BotPawnClass or BotPawnBlueprint?

And another question: What would I do, if I also wanted to find C++ classes with FClassFinder? How would I do that? Do I just pass in the class name? I can’t possibly pass in a “path” to my C++ path, or can I?