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Cannot overload operator: 'operator <<' is ambiguous

I'm trying to overload the << operator, as per Rama's wiki tutorial about binary saving, so that I can save a custom object to binary.

I have created a separate header file for operator overloading called FileOperators.h which contains this:

 FORCEINLINE FArchive& operator<<(FArchive& Ar, USettings* Settings)
     if (!Settings) return Ar;
     Ar << Settings->ObjectClass;
     return Ar;

So it should save the ObjectClass parameter (UClass*) to binary. And I have created a function trying to use that (I'm only putting the relavant line in here)

 void UFileSystem::SaveLoadData(FArchive& Ar, USettings* Settings)
     Ar << Settings;

When I try to compile, I get the error: 'operator <<' is ambiguous

If I mouse over the << operator, it tells me why:

 more than one operator "<<" matches these operands:
 function "operator<<(FArchive &Ar, USettings *&Res)"
 function "operator<<(FArchive &Ar, USettings *Settings)"
 oparand types are: FArchive << USettings*

What am I doing wrong? I can't see that I'm doing anything differently from Rama's code...

Product Version: UE 4.17
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asked Oct 24 '17 at 08:53 PM in C++ Programming

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1 answer: sort voted first

I figure it out.

The operator override needed to be

USettings& Settings


USettings* Settings

And the use of the operator needed to be:

Ar << *Settings


Ar << Settings

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answered Oct 25 '17 at 07:52 AM

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