How to edit Blueprint default variable via editor scripting?

[CabbageOni]

Hello, I’m trying to make an EditorUtilityWidget where if I press a button, it changes certain default values of a blueprint.

Is there a way to achieve this (possibly w/o c++)?

[KristofMorva (Kristóf Morva)]

The only semi-BP solution I remember is using the SetEditorProperty on the ClassDefaultObject (which I exposed from C++), but as far as I remember, this editor utility function was only added in 4.26.

[UE_FlavienP]

An alternative through python. You can run python script through blueprints.

import unreal

bp_object = unreal.EditorAssetLibrary.load_blueprint_class('/game/BP_Modif_Default')
bp_default_oject = unreal.get_default_object(bp_object)
bp_default_oject.set_editor_property("age",21)

[CabbageOni]

This seems to be the solution, yet I can’t test 'em since my project is at .24
Might have to consider migrating, thanks a lot!

[CabbageOni]

Thank you for the suggestion, but I am looking for the in-EditorUtilityWidget availability as of now.

[mindblender]

Thanks! It worked! Exposing class defaults via C++ was a must.

[deyama2012]

I know it’s an old thread, but is there a way to set default values of actor components’ variables? It just doesn’t seem we have access to components through default object, right?

[fael097]

I’m trying to figure this out, but no dice yet.

A simple “this isn’t possible” would do

[Kiry]

Leaving info here for people who will come after me

Easiest Way it to expose some minor C++ functions that i could not find in BP:

• Access Actor Blueprint CDO needed to edit Blueprint default values .
• Access Components Templates to edit subcomponents default values within selected blueprint;

Expose using BPFL

C++ code

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"

#include "Engine/SCS_Node.h"
#include "Engine/SimpleConstructionScript.h"

#include "GridEditing_Statics.generated.h"

/**
 * 
 */
UCLASS()
class PROJECT_API UEditorHelper_Statics : public UBlueprintFunctionLibrary
{
    GENERATED_BODY()

    UFUNCTION(BlueprintCallable)
    static UObject* GetClassDefaultObject(TSubclassOf<UObject> InClass)
    {
       if (InClass)
        {
           return InClass->GetDefaultObject<UObject>();
        }
        return nullptr;
    }
    
    UFUNCTION(BlueprintCallable)
    static TArray<UActorComponent*> GetComponentTemplatesFromActorClass(TSubclassOf<AActor> InActorClass, TSubclassOf<UActorComponent> InComponentClass)
    {
       if (InActorClass && InComponentClass)
        {
           if (UBlueprintGeneratedClass* ActorBlueprintGeneratedClass = Cast<UBlueprintGeneratedClass>(InActorClass))
           {
              if (auto ConstructionScript = ActorBlueprintGeneratedClass->SimpleConstructionScript)
              {
                 TArray<UActorComponent*> ResultComp;
                 for (const USCS_Node* const Node : ConstructionScript->GetAllNodes())
                 {
                    auto ComponentTemplat = Node->GetActualComponentTemplate(ActorBlueprintGeneratedClass);
    
                    if (ComponentTemplat && ComponentTemplat->GetClass() == InComponentClass)
                    {
                       ResultComp.Add(ComponentTemplat);
                    }
                 }
    
                 return ResultComp;
              }
           }
        }
    
        return TArray<UActorComponent*>();
    }
};

To Edit Actor CDO with Bluetility

To Edit Component Templates with Bluetility