L160. Getting an error message when using/moving constructor

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#1

When I move the UTankAimingComponent() constructor to private:, I get these compile erros:

CompilerResultsLog:Error: Error Tank.cpp.obj : error LNK2019: unresolved external symbol "private: __cdecl UTankAimingComponent::UTankAimingComponent(void)" (??0UTankAimingComponent@@AEAA@XZ) referenced in function "public: static void __cdecl UTankAimingComponent::__DefaultConstructor(class FObjectInitializer const &)" (?__DefaultConstructor@UTankAimingComponent@@SAXAEBVFObjectInitializer@@@Z)
CompilerResultsLog:Error: Error TankAimingComponent.cpp.obj : error LNK2001: unresolved external symbol "private: __cdecl UTankAimingComponent::UTankAimingComponent(void)" (??0UTankAimingComponent@@AEAA@XZ)
CompilerResultsLog:Error: Error BattleTank.generated.cpp.obj : error LNK2001: unresolved external symbol "private: __cdecl UTankAimingComponent::UTankAimingComponent(void)" (??0UTankAimingComponent@@AEAA@XZ)

But if I comment the constructor out completely, the code compiles fine.
Similarly, I tried to create a constructor in the TankMovementComponent, but kept getting similar errors, so I compiled without a constructor.
What could be causing this? (I’m using UE version 4.12.5.)

#2

If the constructor is private that means only functions within the class or friends can call it. Meaning that you wouldn’t be able to just instantiate the class normally.

#3

I get the same errors when I leave the constructor in public:
I have to completely comment the constructor out to get the code to compile…

#4

Wait, I just looked at my code and I have it private. Re-reading the error message again… By any chance did you declare the constructor in the header file and then never defined it in the source file?

#5

It seems to have been the case. I had the constructor definition commented out.
Then I wonder why the code still compiled and the program ran without the constructor. Is the constructor not necessary, then?

#6

If one isn’t provided one will be auto generated by the compiler.

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