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How do I correctly use pointers in this situation?


I'm desperately trying to remember C++ right now and I have stumbled across this problem.

I'm trying to deserealize data from JSON for which I am using UE4 libraries.

Consider the signature for the FJsonObject::TryGetArrayField method that I am trying to use:

 bool TryGetArrayField
     const FString & FieldName,
     const TArray < TSharedPtr < FJsonValue > > *& OutArray

This code works if I pass a variable declared as const TArray<TSharedPtr<FJsonValue>> *OutArray as the second parameter, but leaves me wondering about 2 things:

1) Isn't there a better way to use pointers in case of "OutArray" variable? Can I avoid using the native const "*" pointer here and use a smart pointer instead? Using TSharedPtr<TArray<TSharedPtr<FJsonValue>>> OutArray gives me compile time errors about assigning temporary object to a reference.

2) Why does trying to delete "OutArray" pointer later on gives me an exception at runtime? Does that mean UE4's GC manages this pointer for me? How can I be aware if data reference by "*" pointer is managed by GC if it's not an explicit "UPROPERTY()"?.

Thanks in advance.

Product Version: UE 4.16
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asked Aug 28 '17 at 12:05 PM in C++ Programming

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avatar image UnrealDev00 Sep 16 '17 at 07:10 PM

I have the exact same question...

OutArray should just be a reference to a pointer that is pointing to a const TArray.

So if I pass in a const TArray<TSharedPtr<FJsonValue>> *myOutArray to FJsonObject::TryGetArrayField, when it returns myOutArray will be pointing to memory somewhere. Who's managing that memory?

Maybe I just suck at C++ and I'm missing something?

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