Error LNK2001 Unresolved external symbol

Development Programming & Scripting
1

I’m getting the error and its frustrating me because I have no idea whats wrong, if anyone could help I would really appreciate it!

CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2001: unresolved external symbol "public: virtual bool __cdecl FHttpModule::Exec(class UWorld *,wchar_t const *,class FOutputDevice &)" (?Exec@FHttpModule@@UEAA_NPEAVUWorld@@PEB_WAEAVFOutputDevice@@@Z)
CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2019: unresolved external symbol "public: virtual class TSharedRef<class IHttpRequest,0> __cdecl FHttpModule::CreateRequest(void)" (?CreateRequest@FHttpModule@@UEAA?AV?$TSharedRef@VIHttpRequest@@$0A@@@XZ) referenced in function "private: void __cdecl UCustomblueprintfunctionlib
rary::HttpRequest(void)" (?HttpRequest@UCustomblueprintfunctionlibrary@@AEAAXXZ)
CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2001: unresolved external symbol "private: virtual void __cdecl FHttpModule::StartupModule(void)" (?StartupModule@FHttpModule@@EEAAXXZ)
CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2001: unresolved external symbol "private: virtual void __cdecl FHttpModule::PostLoadCallback(void)" (?PostLoadCallback@FHttpModule@@EEAAXXZ)
CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2001: unresolved external symbol "private: virtual void __cdecl FHttpModule::PreUnloadCallback(void)" (?PreUnloadCallback@FHttpModule@@EEAAXXZ)
CompilerResultsLog:Error: Error Customblueprintfunctionlibrary.cpp.obj : error LNK2001: unresolved external symbol "private: virtual void __cdecl FHttpModule::ShutdownModule(void)" (?ShutdownModule@FHttpModule@@EEAAXXZ)
CompilerResultsLog:Error: Error C:\Users\RG STUDIOS\Documents\Unreal Projects\MyProject2\Binaries\Win64\UE4Editor-MyProject2-8046.dll : fatal error LNK1120: 6 unresolved externals

// Fill out your copyright notice in the Description page of Project Settings.

#include "MyProject2.h"
#include "Http.h"
#include "Json.h"
#include "Customblueprintfunctionlibrary.h"

bool UCustomblueprintfunctionlibrary::GetYoutubeUrls(FString Url, TArray<FString>& UrlArray)
{

	return FFileHelper::LoadANSITextFileToStrings(*(FPaths::GameDir() + Url), NULL, UrlArray);
}
/**UCustomblueprintfunctionlibrary::constructt(const class FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
	//When the object is constructed, Get the HTTP module
	Http = &FHttpModule::Get();
}**/

void UCustomblueprintfunctionlibrary::HttpRequest()
{
	TSharedRef<IHttpRequest> Request = FHttpModule().Get().CreateRequest();
	Request->OnProcessRequestComplete().BindUObject(this, &UCustomblueprintfunctionlibrary::OnResponseReceived);
	//This is the url on which to process the request
	Request->SetURL("http://localhost:8081/WebApi/getint.php");
	Request->SetVerb("GET");
	Request->SetHeader(TEXT("User-Agent"), "X-UnrealEngine-Agent");
	Request->SetHeader("Content-Type", TEXT("application/json"));
	Request->ProcessRequest();
	FString complete = "swag";
}
void UCustomblueprintfunctionlibrary ::OnResponseReceived(FHttpRequestPtr Request, FHttpResponsePtr Response, bool bWasSuccessful)
{

	//Create a pointer to hold the json serialized data
	TSharedPtr<FJsonObject> JsonObject;

	//Create a reader pointer to read the json data
	TSharedRef<TJsonReader<>> Reader = TJsonReaderFactory<>::Create(Response->GetContentAsString());

	//Deserialize the json data given Reader and the actual object to deserialize
	if (FJsonSerializer::Deserialize(Reader, JsonObject))
	{
		//Get the value of the json object by field name
		int32 recievedInt = JsonObject->GetIntegerField("customInt");

		//Output it to the engine
		FString File = FString::FromInt(recievedInt);
	}
}

MY .H File

#include "Kismet/BlueprintFunctionLibrary.h"
#include "Http.h"
#include "Json.h"
#include "Customblueprintfunctionlibrary.generated.h"

/**
 * 
 */
UCLASS()
class MYPROJECT2_API UCustomblueprintfunctionlibrary : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()
private:

	UFUNCTION(BlueprintPure, Category = "GetUrls")
		static bool GetYoutubeUrls(FString Url, TArray<FString>& UrlArray);
	/* The actual HTTP call */
	UFUNCTION()
		void HttpRequest();
	/*constructt(const class FObjectInitializer& ObjectInitializer);*/

	/*Assign this function to call when the GET request processes sucessfully*/
		void OnResponseReceived(FHttpRequestPtr Request, FHttpResponsePtr Response, bool bWasSuccessful);

};
2

Hi Legacy379 ,

I believe you forgot to add the HTTP module to your dependencies in your build.cs file.

Hope that helps. Cheers,

3

Have you added HTTP to the PublicDependencyModuleNames in your x.build.cs file?

4

yeah I do have it added I have it setup like this:

using UnrealBuildTool;

public class MyProject2 : ModuleRules
{
	public MyProject2(TargetInfo Target)
	{
		PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "Http", "Json", "JsonUtilities" });

		PrivateDependencyModuleNames.AddRange(new string[] {  });

		// 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
	}
}
5

Hey,
I do have it added in my build.css file like this

using UnrealBuildTool;

public class MyProject2 : ModuleRules
{
	public MyProject2(TargetInfo Target)
	{
		PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "Http", "Json", "JsonUtilities" });

		PrivateDependencyModuleNames.AddRange(new string[] {  });

		// 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
	}
}
6

Hi, I can currently not verify it, but iI would try to UPERCASE the HTTP because the module is named uppercase.

7

Hey I already tried that, I changed it in the dependency, didnt work so uppercased the #include “HTTP.h” but that also didnt work, same problem

8

Could you try including HttpModule.h in your source as well?

9

Ok so I finally fixed it, the problem was with:

TSharedRef<IHttpRequest> Request = FHttpModule().Get().CreateRequest();

I replaced it with:

FHttpModule * http = &FHttpModule::Get();
TSharedRef<IHttpRequest> Request = http->CreateRequest();
10

thank you ( :