Error LNK2001: unresolved external symbol with almost empty class

Development Platform & Builds
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1

Hi,

Here is my class def :
#pragma once
#include “CoreMinimal.h”
#include “UObject/NoExportTypes.h”
#include “MyObject.generated.h”

/**
*
*/
UCLASS(Blueprintable)

class UDEMY_PROJ1_CPP_API UMyObject : public UObject

{
GENERATED_BODY()

public:

UMyObject();

};

And the error is:

1>------ Build started: Project: UE4, Configuration: BuiltWithUnrealBuildTool Win32 ------
2>------ Build started: Project: udemy_proj1_cpp, Configuration: Development_Editor x64 ------
2>Creating makefile for udemy_proj1_cppEditor (game project files are newer)
2>Deleted hot-reload file: C:\DEV\ueprojets\udemy_proj1_cpp\Intermediate\Build\Win64\UE4Editor\Development\udemy_proj1_cpp\UE4Editor-udemy_proj1_cpp-0001.lib
2>Building udemy_proj1_cppEditor…
2>Using Visual Studio 2019 14.25.28614 toolchain (C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.25.28610) and Windows 10.0.18362.0 SDK (E:\Windows Kits\10).
2>Building 3 actions with 8 processes…
2> [1/3] UE4Editor-udemy_proj1_cpp.lib
2> Creating library C:\DEV\ueprojets\udemy_proj1_cpp\Intermediate\Build\Win64\UE4Editor\Development\udemy_proj1_cpp\UE4Editor-udemy_proj1_cpp.lib and object C:\DEV\ueprojets\udemy_proj1_cpp\Intermediate\Build\Win64\UE4Editor\Development\udemy_proj1_cpp\UE4Editor-udemy_proj1_cpp.exp
2> [2/3] UE4Editor-udemy_proj1_cpp.dll
2> Creating library C:\DEV\ueprojets\udemy_proj1_cpp\Intermediate\Build\Win64\UE4Editor\Development\udemy_proj1_cpp\UE4Editor-udemy_proj1_cpp.suppressed.lib and object C:\DEV\ueprojets\udemy_proj1_cpp\Intermediate\Build\Win64\UE4Editor\Development\udemy_proj1_cpp\UE4Editor-udemy_proj1_cpp.suppressed.exp

2>MyObject.cpp.obj : error LNK2019: unresolved external symbol “public: __cdecl UMyObject::UMyObject(void)” (??0UMyObject@@QEAA@XZ) referenced in function “public: static void __cdecl UMyObject::__DefaultConstructor(class FObjectInitializer const &)” (?__DefaultConstructor@UMyObject@@SAXAEBVFObjectInitializer@@@Z)

2>MyObject.gen.cpp.obj : error LNK2001: unresolved external symbol “public: __cdecl UMyObject::UMyObject(void)” (??0UMyObject@@QEAA@XZ)

2>C:\DEV\ueprojets\udemy_proj1_cpp\Binaries\Win64\UE4Editor-udemy_proj1_cpp.dll : fatal error LNK1120: 1 unresolved externals

2>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.MakeFile.Targets(44,5): error MSB3073: The command “C:\DEV\UE\UE_4.25\Engine\Build\BatchFiles\Build.bat udemy_proj1_cppEditor Win64 Development -Project=“C:\DEV\ueprojets\udemy_proj1_cpp\udemy_proj1_cpp.uproject” -WaitMutex -FromMsBuild” exited with code 6.

2>Done building project “udemy_proj1_cpp.vcxproj” – FAILED.
========== Build: 1 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

2

Ok, so I HAD TO IMPLEMENT the methods in the .cpp file.
like this:

UMyObject::UMyObject()
{

}

And now it compiles, also note that I changed the compile from x64 to win32, don’t know if it is useful though.