Question

Background worker, passing variables are not working, in my example I explain everything, I put only the functions that were important, I have the other functions from the BackgroundWorker.

int TheFunction(unordered_map<std::string,std::string> options, BackgroundWorker^ worker, DoWorkEventArgs ^ e){

    if(options["option1"].compare("options") == 0){
            //...
        }

        return 0;
}

    void backgroundWorker2_DoWork(Object^ sender, DoWorkEventArgs^ e ){
         BackgroundWorker^ worker = dynamic_cast<BackgroundWorker^>(sender);     
        //e->Result = TheFunction( safe_cast<Int32>(e->Argument), worker, e ); //That's how I do to send an integer value and works just fine, but I don't know how to send non-numeric values with safe_cast or something that works, in the function it looks like this: TheFunction(int index, ...) it works fine, I want to know with unordered_map or with strings also would work, I want more than one argument if you can do with std::string
          e->Result = TheFunction(safe_cast<unordered_map<std::string,std::string>>(e->Argument)); //I tried this, and it didn't work

    }


void CallBackgroundWorker(){
         this->backgroundWorker2 = gcnew System::ComponentModel::BackgroundWorker;
         this->backgroundWorker2->WorkerReportsProgress = true;
         this->backgroundWorker2->WorkerSupportsCancellation = true;
         this->backgroundWorker2->DoWork += gcnew DoWorkEventHandler( this, &GUISystem::backgroundWorker2_DoWork );
         this->backgroundWorker2->RunWorkerCompleted += gcnew RunWorkerCompletedEventHandler( this, &GUISystem::backgroundWorker2_RunWorkerCompleted );
         this->backgroundWorker2->ProgressChanged += gcnew ProgressChangedEventHandler( this, &GUISystem::backgroundWorker2_ProgressChanged );


         unordered_map<std::string,std::string>* options = unordered_map<std::string,std::string>();
         options["option1"] = "valor1";
         options["option2"] = "valor2";

         this->backgroundWorker2->RunWorkerAsync(options);
}

So how do I do to send the unordered_map or a std::string (more than 1 arguments) ?

thanks in advance. that would help a lot.

Answer 1

This line:

unordered_map<std::string,std::string>* options = unordered_map<std::string,std::string>();

isn’t legal even in standard C++. A pointer needs to store an address, not an object. So probably you meant to say new to use dynamic allocation (after all, the object needs to survive until the callback runs on the other thread).

At that point, you can wrap the pointer inside System::IntPtr, and in the callback, cast the result of ToPointer().