Error C2227: left of '->SpawnActor' must point to class/struct/union/generic type UE4

Development Programming & Scripting
1

I created maze generation lib, but when I try to compile, it returns error:

CompilerResultsLog: Error: D:\Home\Volodya\Projects\Games\UE4\TestingSomething\Something\Source\Something\Private\MazeLib.cpp(17) : error C2352: 'UObject::GetWorld': illegal call of non-static member function
CompilerResultsLog: Error: C:\Program Files\Epic Games\UE_4.18\Engine\Source\Runtime\CoreUObject\Public\UObject/Object.h(473) : note: see declaration of 'UObject::GetWorld'
CompilerResultsLog: Error: D:\Home\Volodya\Projects\Games\UE4\TestingSomething\Something\Source\Something\Private\MazeLib.cpp(17) : error C2227: left of '->SpawnActor' must point to class/struct/union/generic type
CompilerResultsLog: Error: D:\Home\Volodya\Projects\Games\UE4\TestingSomething\Something\Source\Something\Private\MazeLib.cpp(17) : error C2227: left of '->GetAuthoritativeClass' must point to class/struct/union/generic type
CompilerResultsLog: ERROR: UBT ERROR: Failed to produce item: D:\Home\Volodya\Projects\Games\UE4\TestingSomething\Something\Binaries\Win64\UE4Editor-Something-5058.dll

My spawnMaze function in cpp file:

void UMazeLib::spawnMaze(int size) {
	bool** maze = generateMaze(size);
	for (int h = 0; h < size; h++)
	{
		maze[h] = new bool[size];
		for (int w = 0; w < size; w++)
		{
			const FVector* position = new FVector(10 * h, 10 * w, 0);
			GetWorld()->SpawnActor(wallClass->GetAuthoritativeClass(), position);
		}
	}
}

and my .h file:

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "Wall.h"
#include "MazeLib.generated.h"

/**
 * 
 */
UCLASS()
class SOMETHING_API UMazeLib : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()
	
	public:	
		UFUNCTION(BlueprintCallable, Category = "Something")
		static void spawnWall(FTransform str);

		UFUNCTION(BlueprintCallable, Category = "Maze")
		static void spawnMaze(int size);

		UPROPERTY(BlueprintReadWrite, EditAnywhere)
		TSubclassOf<class AWall> wallClass;

		UPROPERTY(BlueprintReadWrite, EditAnywhere)
		UWorld* world = GetWorld();

	private:
		static	bool** generateMaze(int size);
};
2

A static function has no “this” object so you can’t call GetWorld(). You either need to make it non-static or pass in the actor pointer as a parameter.

3

Yeah, but when I make function spawnMaze() non-static, it’s hiding in level Blueprint.

4

Yes, I only remove ‘static’ from declaration.

5

That should be possible. What does your code look like? You just removed the static keyword from the function declaration?

6

Oh it’s a function library. For some reason I thought it was a level BP. I don’t have much experience with function libraries, but if it has to be static then just pass the world as a function parameter instead of calling GetWorld() inside the function. When you call the function, you can pass in GetWorld().

7

So, I have to add world object as function parameter. But why I can’t use non-static methods threre. So my function must be like this: static void spawnMaze(int size, UWorld* world)?

8

You can’t use non-static members from a static function. You need an object to work with. There’s no way I can explain it better than the references available online. I found this one, for example

And yes, that function should work. It looks like you have to use static functions so passing in parameters is the only way to go.

9

Did it work out for you? If not, let me know. If so, please close the question (check-mark under the up/down-vote widget). By the way, if at any time one of your parameters is an AActor then you can call GetWorld() from that (and save an extra parameter).