Gloval variable in C++ Winform

Question

Gloval variable in C++ Winform

José Carlos 886

Good morning friends.

I have a small application for my own use developed in C++ Winforms. The application has only two forms. One main with menu and another with operations. I need to create a global variable on the main form, but that I can change its value on the other form and return that value to the main form.

In the main form I put static int flag; When I use the variable in the other form it gives an error message saying: flag::undeclared identifier.

How to solve it?

Thanks

David Lowndes 4,726 Reputation points

2022-12-12T16:27:21.43+00:00

Show what you've done, don't let us have to guess.

2 answers

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David Lowndes 4,726 Reputation points

2022-12-12T16:27:21.43+00:00

Show what you've done, don't let us have to guess.

Answer 1

YujianYao-MSFT 4,296 Microsoft External Staff

Hi @Anonymous ,

Did you make the two header files include each other?

Doing so will lead to the problem you mentioned, I suggest you refer to the solution in this issue.

Best regards,

Elya

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José Carlos 886 Reputation points

2022-12-13T12:28:18.717+00:00

OK.
I'll try here. I've written a lot of programs in C#, but I'm looking to move some to C++ Winforms.
C# has no concept of global variable but static class. I tried to make a static class in C++ but different from C#> I couldn't.
I will try this alternative from the link you sent me.
Thank you very much.
Anything, let me know here.

José Carlos]
YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-12-14T09:31:53.96+00:00

Hi @Anonymous ,

Regarding C++ classes, I suggest you read this document. And this document introduces the static keyword in C++, I believe it will be helpful to you.

YujianYao-MSFT 4,296 Microsoft External Staff

Hi @Anonymous ,

In order to avoid undeclared identifiers, you need to avoid header files including each other. So you need to put the function declaration in .h file and write the function implementation in .cpp file.

Sample

MyForm1.h

 //Generate a click event after double-clicking the button  
 //modify it to a function declaration  
  private:  
         System::Void button1_Click(System::Object ^ sender,  
                                    System::EventArgs ^ e);

MyForm1.cpp

 #include "MyForm.h"  
 #include "MyForm1.h"  
 using namespace System;  
 using namespace System::ComponentModel;  
 using namespace System::Collections;  
 using namespace System::Windows::Forms;  
 using namespace System::Data;  
 using namespace System::Drawing;  
  System::Void Project50::MyForm1::button1_Click(System::Object ^ sender,  
                                     System::EventArgs ^ e) {  
     Project50::MyForm ^ form1 =  
        (Project50::MyForm ^) Application::OpenForms["MyForm"];  
     form1->txt1->Text = textBox1->Text;  
     form1->txt2->Text = textBox2->Text;  
  }

Answer 2

José Carlos 886

Hello
I put it in the topic already answered by you in the article "Update textbox on another form - C++ Winforms" with a screen example, because this solution does not suit me. Did not work. I believe it's the type of application. Take a look at my question, because I think you will understand and for sure you will get the ultimate solution for me.
Thanks a lot again.

YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-12-16T06:59:26.58+00:00

Hi @Anonymous ,

Could you please provide a minimal executable that reproduces this problem? This helps everyone to solve your problem.

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Gloval variable in C++ Winform

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