Can't access global variables - winforms

Question

In globaldata.h I am defining a typedef struct as GlobalData. In my main cpp program, I'm including globaldata.h, then declaring
GlobalData globalData;
After that declaration, I include createNetDialog.h and gui.h. Why can I only reference globalData in gui.h but not createNetDialog.h? Both include files should be pasted into my .cpp file during precompile, so globalData should be visible in both right?
I have a GlobalData structure defined here:
globaldata.h
typedef struct {
string netFilename;
DataFileReader *dataFileReader;
} GlobalData;
In my c++ code, I have:
gui.cpp
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <string>
#include "DataFileReader.h"
#include "globaldata.h"
GlobalData globalData;
#include "createNetDialog.h"
#include "gui.h"
using namespace System;
using namespace System::Windows::Forms;
using namespace std;
[STAThread]
void Main(array<String^>^ args)
{
Application::EnableVisualStyles();
Application::SetCompatibleTextRenderingDefault(false);
Carnac::gui formMain;
Application::Run(%formMain);
}
createNetDialog.h (in the createNetDialog constructor)
#pragma once
namespace Carnac {
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 createNetDialog
/// </summary>
public ref class createNetDialog : public System::Windows::Forms::Form
{
public:
createNetDialog(void)
{
InitializeComponent();
// left of '.size' must have a class/struct/union
// left of '.dataFileReader' must have a class/struct/union
// 'globalData':undeclared identifier despite being declared right before
// this file is included in the .cpp file
for (unsigned int i=0; i<globalData.dataFileReader->_headerItems.size(); i++)
{
// do something
}
}
protected:
/// <summary>
/// Clean up any resources being used.
/// </summary>
~createNetDialog()
{
if (components)
{
delete components;
}
}
protected:
protected:
private: System::Windows::Forms::Button^ buttonCreate;
private: System::Windows::Forms::Button^ buttonCreateCancel;
private:
System::ComponentModel::Container ^components;
#pragma region Windows Form Designer generated code
void InitializeComponent(void)
{
this->buttonCreate = (gcnew System::Windows::Forms::Button());
this->buttonCreateCancel = (gcnew System::Windows::Forms::Button());
this->SuspendLayout();
//
// buttonCreate
//
this->buttonCreate->Anchor = static_cast<System::Windows::Forms::AnchorStyles>((System::Windows::Forms::AnchorStyles::Bottom | System::Windows::Forms::AnchorStyles::Left));
this->buttonCreate->Location = System::Drawing::Point(16, 288);
this->buttonCreate->Name = L"buttonCreate";
this->buttonCreate->Size = System::Drawing::Size(75, 23);
this->buttonCreate->TabIndex = 7;
this->buttonCreate->Text = L"Create";
this->buttonCreate->UseVisualStyleBackColor = true;
//
// buttonCreateCancel
//
this->buttonCreateCancel->Anchor = static_cast<System::Windows::Forms::AnchorStyles>((System::Windows::Forms::AnchorStyles::Bottom | System::Windows::Forms::AnchorStyles::Right));
this->buttonCreateCancel->Location = System::Drawing::Point(404, 288);
this->buttonCreateCancel->Name = L"buttonCreateCancel";
this->buttonCreateCancel->Size = System::Drawing::Size(75, 23);
this->buttonCreateCancel->TabIndex = 8;
this->buttonCreateCancel->Text = L"Cancel";
this->buttonCreateCancel->UseVisualStyleBackColor = true;
this->buttonCreateCancel->Click += gcnew System::EventHandler(this, &createNetDialog::buttonCreateCancel_Click);
//
// createNetDialog
//
this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
this->ClientSize = System::Drawing::Size(491, 323);
this->Controls->Add(this->buttonCreateCancel);
this->Controls->Add(this->buttonCreate);
this->Name = L"createDialog";
this->Text = L"CreateDialog";
this->ResumeLayout(false);
this->PerformLayout();
}
#pragma endregion
private: System::Void buttonCreateCancel_Click(System::Object^ sender, System::EventArgs^ e)
{
this->Close();
}
};
}
gui.h (at the end)
#pragma once
#include <msclr\marshal_cppstd.h>
namespace Carnac {
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 gui
/// </summary>
public ref class gui : public System::Windows::Forms::Form
{
public:
gui(void)
{
InitializeComponent();
//
//TODO: Add the constructor code here
//
}
protected:
/// <summary>
/// Clean up any resources being used.
/// </summary>
~gui()
{
if (components)
{
delete components;
}
}
protected:
private: int _dataColumnSelected;
private: System::Windows::Forms::Button^ buttonLoad;
private:
/// <summary>
/// Required designer variable.
/// </summary>
System::ComponentModel::Container ^components;
#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent(void)
{
this->buttonLoad = (gcnew System::Windows::Forms::Button());
this->SuspendLayout();
//
// buttonLoad
//
this->buttonLoad->Anchor = static_cast<System::Windows::Forms::AnchorStyles>((System::Windows::Forms::AnchorStyles::Bottom | System::Windows::Forms::AnchorStyles::Left));
this->buttonLoad->Text = L"Load Data";
this->buttonLoad->UseVisualStyleBackColor = true;
this->buttonLoad->Click += gcnew System::EventHandler(this, &gui::buttonLoad_Click);
this->buttonLoad->Location = System::Drawing::Point(67, 66);
this->buttonLoad->Name = L"buttonLoad";
this->buttonLoad->Size = System::Drawing::Size(75, 23);
this->buttonLoad->TabIndex = 0;
this->buttonLoad->UseVisualStyleBackColor = true;
//
// gui
//
this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
this->BackColor = System::Drawing::SystemColors::AppWorkspace;
this->ClientSize = System::Drawing::Size(234, 171);
this->Controls->Add(this->buttonLoad);
this->Name = L"gui";
this->Text = L"Carnac";
this->ResumeLayout(false);
}
#pragma endregion
static std::string toStandardString(System::String^ string)
{
using System::Runtime::InteropServices::Marshal;
System::IntPtr pointer = Marshal::StringToHGlobalAnsi(string);
char* charPointer = reinterpret_cast<char*>(pointer.ToPointer());
std::string returnString(charPointer, string->Length);
Marshal::FreeHGlobal(pointer);
return returnString;
}
private: System::Void buttonPredictRun_Click(System::Object^ sender, System::EventArgs^ e)
{
}
private: System::Void buttonTestLoad_Click(System::Object^ sender, System::EventArgs^ e)
{
}
private: System::Void buttonLoad_Click(System::Object^ sender, System::EventArgs^ e)
{
OpenFileDialog^ openFileDialog1 = gcnew OpenFileDialog;
openFileDialog1->Filter = "Data Files|*.dat";
if (openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK)
{
ifstream inFile;
String^ strfilename = openFileDialog1->InitialDirectory + openFileDialog1->FileName;
// THIS WORKS
// Why can I use globalData here but not in createNetDialog.h?
globalData.dataFileReader = new DataFileReader(toStandardString(strfilename));
}
}
};
}
Thanks for any help

Answer 1

Yes, globalData is visible in both gui.h and createNetDialog.h, when compiled from gui.cpp. In globalData.h all you have defined is a type, not a global variable of that type. When compiled from any other cpp file, gui.h and createNetDialog.h can't see the declaration of the global variable in gui.cpp.
Here's what you want to do: declare both the type, and an extern global variable in globalData.h. Include globalData.h from every file you want to use it in, don't rely on other files to have included it before the one you want to use it in. In just one cpp file (currently gui.cpp), declare the actual global variable.
// globalData.h
#include "DataFileReader.h"
typedef struct {
string netFilename;
DataFileReader *dataFileReader;
} GlobalData;
extern GlobalData globalData;
.
// EVERY file where you use globalData
#include "globalData.h"
.
// gui.cpp
#include "globaldata.h"
GlobalData globalData;