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C++/CLI collection issues

Kalithro (2)
I can't for the life of me find an example of a "Managed" form of collection in C++ that allows me to store a collection of created class objects.

I have a simple class. Vehicle. A user fills out a winform that I have created that they enter the Name of the Vehicle in one Textbox and the miles in another Textbox. They press a button... magic. Nope, b/c I'm too stupid to figure out vectors and C++/ managed requirements.

I created a class VehicleCollection. It has std::vector<Vehicle> vehicleList. I have an add function, remove function, a find function, a return Vehicle object function, etc...

I can only create "VehicleCollection" objects in the code where the button is pushed. This of course goes out of scope and I'm stuck. I try initialize above and it tells me I can't (managed class un-managed variable... blah blah blah).

With a string I got around this by:
String ^ vName;

doing whatever that "^" does worked. I can't however do that for some reason with my class.

I have been working on code for 18+ hours non-stop.

What the heck is the deal with managed and non-managed. I just want to make a collection of my vehicle objects to use later across all form objects. I can't figure out List and Collections b/c I don't understand namespace b/c we stopped at ch7 for this class and the book said they would explain in in ch23.

I just want a global variable of a collection of Vehicle. I keep clicking the "Code" button to put my code in but it isn't doing anything. What else today? I had to go to Chrome to get this to work... yep Edge (thanks).
Kalithro (2)
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// Form Class- Mostly generated by VS
// No matter how hard I try... I can't work with a managed class.  Un-Managed vs Managed + Pointers = C++ Nightmares!

#pragma once

#include "Vehicle.h"
#include "VehicleCollection.h"
#include <vector>
#include <msclr\marshal_cppstd.h>

namespace cppVehicleMaintenanceLog {

	using namespace System;
	using namespace System::ComponentModel;
	using namespace System::Collections;
	using namespace System::Windows::Forms;
	using namespace System::Data;
	using namespace System::Drawing;

	/// <summary>
	/// Summary for MyForm
	/// </summary>
	public ref class MyForm : public System::Windows::Forms::Form
	{
	public:
		MyForm(void)
		{
			InitializeComponent();
			//
			//TODO: Add the constructor code here
			//
		}

	protected:
		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		~MyForm()
		{
			if (components)
			{
				delete components;
			}
		}

// Removed a bunch of form stuff...


	private:
		// My added variables
		//
		String ^ vName;
		Double ^ vMiles;
		String ^ mName;
		String ^ mAction;

  // I need a Collection Variable Here
		// Here <vector> nope...

		// Not my code
		System::ComponentModel::Container ^components;

#pragma region Windows Form Designer generated code
// Removed auto generated stuff
#pragma endregion

// Events and my functions

// New Vehicle Menu Item
private: System::Void vehicleToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e) {
	this->pNewVehicle->Show();
	this->pMaintenanceViewer->Hide();
	this->pWelcome->Hide();
	this->bSaveNewVehicle->Enabled = true;
	this->bSaveNewVehicle->Show();
	this->lbNewVehicleList->Enabled = false;
}

// New Maintenance Action
private: System::Void maintenanceActionToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e) {
	this->lblVehicleLoaded->Text = L"" + vName;
	this->pMaintenanceViewer->Show();
	this->pNewVehicle->Hide();
	this->pWelcome->Hide();
}

// Menu Item for loading a vehicle (not creating a new one)
private: System::Void vehicleToolStripMenuItem1_Click(System::Object^  sender, System::EventArgs^  e) {
	this->lbNewVehicleList->Enabled = true;
	this->pNewVehicle->Show();
	this->pMaintenanceViewer->Hide();
	this->pWelcome->Hide();
	this->bSaveNewVehicle->Enabled = false;
	this->bSaveNewVehicle->Hide();

}

// Exit Program
private: System::Void exitProgramToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e) {
	//  Closes the program
	Application::Exit();

}

// Button Press for Save New Vehicle
private: System::Void bSaveNewVehicle_Click(System::Object^  sender, System::EventArgs^  e) {
	// Overall, working in C++ with System::<anything> and std::<anything> is rather confusing.  I hate it and this was my attempt to do right by it.
	// I spend over 11 hours tring to figure out this part
	// The order of what is taught by Deitel is way off for c++
	// Chapter 2 pg. 42- "Namespaces are an advanced C++ feature that we discuss in depth in Chapter 23"
	// They skip talking about one of the most important parts of understanding C programming.  WHY?

	// 3 variables for name, due to not understanding pointers, managed, un-managed.
	vName = tbNewVehicle->Text; // Managed variable vName.
	System::String^ tempVehicleName = vName; // I'm not sure why I needed to do this, but I tried vName in the next line and it failed.
	std::string stdVehicleName = msclr::interop::marshal_as< std::string >(tempVehicleName); // finally a string that I can work with.
	
	// 3 variables for miles, due to not being able to cast a System::String
	String^ tempMilesString = tbNewVehicleMiles->Text;
	double tempMilesDouble = (float)(Convert::ToDouble(tempMilesString));
	vMiles = tempMilesDouble;  // Back to a managed variable
	
	// I tried declairing vList elsewhere but I couldn't figure it out.  Managed vs Un-Managed, can't figure out global public variables.
	// I simply don't know how to reference global variables from elsewhere (maybe just the managed / unmanaged issue).  So static it is.
	// Of course I wish to use this list in other places...
	// I have spent over 10 hours now trying to get a vector list of my objects to work in this crappy managed class, I just don't get it.
	static VehicleCollection vList;

	// Create a vehicle object
	Vehicle newVehicle(stdVehicleName, tempMilesDouble);

	// Now I test if the vehicle is already in the collection
	if (!vList.vehicleExists(stdVehicleName)) {
		vList.addVehicle(newVehicle);
		MessageBox::Show("Vehicle: " + vName + " Miles: " + tempMilesString + " has been added!");
		this->lbNewVehicleList->Items->Add(vName);
		this->tbNewVehicle->Text = L"";
		this->tbNewVehicleMiles->Text = L"";
	}
	else {
		MessageBox::Show("Vehicle: " + vName + " Miles: " + tempMilesString + " already existed and wasn't added!");
	}

	// Spare code, must keep.  Took me 8 hours to figure this all out.

	//newVehicle.setVehicleName("New Name- Mazda");
	//
	//vName = gcnew String(newVehicle.getVehicleName().c_str());
	//MessageBox::Show(vName);
	//
	//
	//newVehicle = vList.findVehicle("Mazda");
	//vName = gcnew String(newVehicle.getVehicleName().c_str());
	//tempVehicleName = vName;
	//stdVehicleName = msclr::interop::marshal_as< std::string >(tempVehicleName);
	//MessageBox::Show(vName);


}

// Managing the NewVehicleList on the pNewVehicle
private: System::Void lbNewVehicleList_SelectedIndexChanged(System::Object^  sender, System::EventArgs^  e) {

// I lose my mind here.  Because I need a global vehicle list.

	 static VehicleCollection vList;  // A static vehicle list

	vName = MyForm::lbNewVehicleList->Text;
	System::String^ tempVehicleName = vName; // I'm not sure why I needed to do this, but I tried vName in the next line and it failed.
	std::string stdVehicleName = msclr::interop::marshal_as< std::string >(tempVehicleName); // finally a string that I can work with.
	this->tbNewVehicle->Text = L"" + vName;
	MessageBox::Show("" + vList.vehicleExists(stdVehicleName));

// this part fails as the list is always empty... 

	if (vList.vehicleExists(stdVehicleName)) {
		Vehicle thisVehicle;
		thisVehicle = vList.findVehicle(stdVehicleName);
		this->tbNewVehicleMiles->Text = L"" + thisVehicle.getVehicleCurrentMiles();
	}
}



};
}
Last edited on
Thomas1965 (4571)
I can only create "VehicleCollection" objects in the code where the button is pushed. This of course goes out of scope and I'm stuck. I try initialize above and it tells me I can't (managed class un-managed variable... blah blah blah).


Normal procedure is to have the "VehicleCollection" as a member variable in the form and create in in the constructor.
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MyForm(void)
{
  InitializeComponent();
	
  //TODO: Add the constructor code here
	
}


In the destructor you delete it.
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/// <summary>
/// Clean up any resources being used.
/// </summary>
~MyForm()
{
  // delete your VehicleCollection if neccessary
  if (components)
  {
	delete components;
  }
}


I can only create "VehicleCollection" objects in the code where the button is pushed. This of course goes out of scope and I'm stuck. I try initialize above and it tells me I can't (managed class un-managed variable... blah blah blah).


When the button is clicked you create your vehicle and add it to the VehicleCollection. If the VehicleCollection is a member of the form it doesn't go out of scope until the form is destroyed.

On code CodeProject you can find some tutorials about C++/CLI or "Managed C++" as it was formerly called.
http://www.codeproject.com/search.aspx?q=c%2B%2B+cli&x=0&y=0&sbo=kw

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