错误LNK2001:未解析的外部符号虚幻引擎4使用插件(UE4)

Question

我正在尝试为UE4导入一个第三方库，并在参与者中使用它。UE4文档建议创建一个插件来实现这一点，并提供了一个自动生成的模板，我目前正在尝试测试这个模板。

我创建了一个空白的C++ UE4项目，其中包含一个新的第三方自定义插件和一个可以在其中使用插件/库的参与者类。

这是我的主要项目的build.cs文件：

// Copyright Epic Games, Inc. All Rights Reserved.

using UnrealBuildTool;

public class TestGame : ModuleRules
{
    public TestGame(ReadOnlyTargetRules Target) : base(Target)
    {
        PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
    
        PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "CustomTestPlugin" });

        PrivateDependencyModuleNames.AddRange(new string[] { "CustomTestPlugin" });
        PublicIncludePaths.AddRange(new string[] { "../Plugins/CustomTestPlugin/Source/CustomTestPlugin/Public" });
        // Uncomment if you are using Slate UI
        // PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });

        // Uncomment if you are using online features
        // PrivateDependencyModuleNames.Add("OnlineSubsystem");

        // To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true
    }
}

并将插件包含在参与者cpp文件中，并使用

#include "CustomTestPlugin.h"

以及在同一个文件中实例化它：

    FCustomTestPluginModule pluggin = FCustomTestPluginModule::FCustomTestPluginModule();

当我在没有上述条件的情况下编译时，它构建得很好，但是当我声明插入变量时，它会出现以下错误：

TestActor.cpp.obj : error LNK2001: unresolved external symbol "public: virtual void __cdecl FCustomTestPluginModule::StartupModule(void)" (?StartupModule@FCustomTestPluginModule@@UEAAXXZ)

H如下所示：

// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "Modules/ModuleManager.h"

class FCustomTestPluginModule : public IModuleInterface
{
public:

    /** IModuleInterface implementation */
    //FCustomTestPluginModule();
    virtual void StartupModule() override;
    virtual void ShutdownModule() override;

private:
    /** Handle to the test dll we will load */
    void*   ExampleLibraryHandle;
};

cpp文件：

// Copyright Epic Games, Inc. All Rights Reserved.

#include "CustomTestPlugin.h"
#include "Core.h"
#include "Modules/ModuleManager.h"
#include "Interfaces/IPluginManager.h"
#include "CustomTestPluginLibrary/ExampleLibrary.h"

#define LOCTEXT_NAMESPACE "FCustomTestPluginModule"


//FCustomTestPluginModule::FCustomTestPluginModule() {
//  UE_LOG(LogTemp, Warning, TEXT("CustomPluConstructed"));
//}

void FCustomTestPluginModule::StartupModule()
{
    // This code will execute after your module is loaded into memory; the exact timing is specified in the .uplugin file per-module

    // Get the base directory of this plugin
    FString BaseDir = IPluginManager::Get().FindPlugin("CustomTestPlugin")->GetBaseDir();

    // Add on the relative location of the third party dll and load it
    FString LibraryPath;
#if PLATFORM_WINDOWS
    LibraryPath = FPaths::Combine(*BaseDir, TEXT("Binaries/ThirdParty/CustomTestPluginLibrary/Win64/ExampleLibrary.dll"));
#elif PLATFORM_MAC
    LibraryPath = FPaths::Combine(*BaseDir, TEXT("Source/ThirdParty/CustomTestPluginLibrary/Mac/Release/libExampleLibrary.dylib"));
#elif PLATFORM_LINUX
    LibraryPath = FPaths::Combine(*BaseDir, TEXT("Binaries/ThirdParty/CustomTestPluginLibrary/Linux/x86_64-unknown-linux-gnu/libExampleLibrary.so"));
#endif // PLATFORM_WINDOWS

    ExampleLibraryHandle = !LibraryPath.IsEmpty() ? FPlatformProcess::GetDllHandle(*LibraryPath) : nullptr;

    if (ExampleLibraryHandle)
    {
        // Call the test function in the third party library that opens a message box
        ExampleLibraryFunction();
    }
    else
    {
        FMessageDialog::Open(EAppMsgType::Ok, LOCTEXT("ThirdPartyLibraryError", "Failed to load example third party library"));
    }
}

void FCustomTestPluginModule::ShutdownModule()
{
    // This function may be called during shutdown to clean up your module.  For modules that support dynamic reloading,
    // we call this function before unloading the module.

    // Free the dll handle
    FPlatformProcess::FreeDllHandle(ExampleLibraryHandle);
    ExampleLibraryHandle = nullptr;
}

#undef LOCTEXT_NAMESPACE
    
IMPLEMENT_MODULE(FCustomTestPluginModule, CustomTestPlugin)

任何解决这一问题的帮助都将不胜感激！

Answer 1

您不需要手动实例化模块。如果在项目中引用该模块，则该模块将在启动时由引擎加载和实例化。

如果由于某种原因需要获得对模块的单例的引用，可以使用

FModuleManager::LoadModuleChecked<FYourModuleType>("YourModule");