Simple programming question C++

Question

2.00/5 (2 votes)

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I am totally new to programming so please forgive me and english is not my first language. I am learning C++ in CLR format so I have the following:

test.h

Declared global variable int x;

C++

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) 
{   
x = 5;
test ( x ) 

}

private: System::Void button2_Click(System::Object^  sender, System::EventArgs^  e) 
{
       test(x) -> Still cannot access the variable x from button1.. :(
}

Update: Created another function in cpp, called it over here in test.h

C++

Function int test ( int i)
{
int i;
return i;
}

Posted 29-Mar-15 18:11pm

justbegin123

Updated 29-Mar-15 22:23pm

CPallini

v2

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Sergey Alexandrovich Kryukov 30-Mar-15 0:38am

There are no "global variables" in .NET. Use class/struct instance members. What are you trying to achieve?
—SA

justbegin123 30-Mar-15 0:49am

Hi Sergey, what I am trying to achieve is , for example button1 variable x has a value of 5.

i want to access the x, which is 5, in button 2 to do something else.

Sergey Alexandrovich Kryukov 30-Mar-15 1:04am

Wrong. There is no such thing as "button variable". Doing something with a variable cannot be your goal. What do you really want to achieve? Really, without mixing your goal with your thoughts on "how". First, "what"?
—SA

justbegin123 30-Mar-15 1:08am

Alright, let me put it in another way.

Let's say I have an int x in button 1, when I clicks it, it will generate out a random number. I want to store that number into x, and redirects the number to button 2, to be able to print out the value. As mentioned, I am new, that might be an excuse, but definitely needing a guidance to start off. Thanks once again.

Sergey Alexandrovich Kryukov 30-Mar-15 1:12am

What is "int x in button 1"? Button is a button, it does not have any int. If you want to generate a random number, do generate it. Your whole approach to thinking is wrong. Your goal cannot be storing something into x, because in write approach (if you are asking a question, you don't know write approach, isn't it logical?), x may or may not exist. Forget about those "variables", explain the behavior.
—SA

justbegin123 30-Mar-15 1:23am

Hi Sergey, Alright. Let me explain my original thought of flow to you. My original idea was to have 2 things.

Step 1) I have a button, that is whenever I click into a panel (Because currently I am operating in C++/CLI), I am able to get the coordinates. I am able to store the coordinates into x. Eg Code: x = e->Location.X;

So for example . x value can be 5, can be 10. whatever, but it is definitely stored into x.

2) So since I have value x from button 1, I will need to use value x to use it in other places.

Do you understand me now? Thanks.

Cheers.

Richard MacCutchan 30-Mar-15 3:49am

The integer x, or whatever other variable you are using, should be declared in your Form class. You can then access it directly in the button event handler. You say you are new to programming, so I would suggest you stop using C++/CLI and switch to C# which is a better choice for Windows Forms.

Sergey Alexandrovich Kryukov 30-Mar-15 11:31am

Maybe. It can be even C++/CLI, but starting with fundamentals and proceed slowly. I would rather say: stop developing UI. None of advanced topic should be started before getting comfortable with the fundamentals. Not understanding variables vs instance (and static, by the way) members is one of the problems of getting clear with fundamentals). It can be better learned on simple console-only applications.
—SA

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Fredrik Bornander · Answer 1 · 2015-03-29T22:10:00

It's a little bit difficult understanding exactly what you want, but I think it's something like this;

When button 1 is pressed, store some value in a variable, somewhere.
When button 2 is pressed, use the value stored by pressing button 1, somehow.

If that's the case something like this might help you get started;

C#

#include "stdafx.h"

#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Windows::Forms;

ref class MyForm : public Form {
private:
    Button^ button1;
    Button^ button2;
    Label^ label;
    int result;

public:
    MyForm();
    void OnClick1(System::Object ^sender, System::EventArgs ^e);
    void OnClick2(System::Object ^sender, System::EventArgs ^e);
};

// Constructor initializing the buttons and label, and adding them to the form
MyForm::MyForm() {
    Text = "My Form";

    button1 = gcnew Button();
    button1->Text = "Button 1 (add 1)";
    button1->SetBounds(10, 10, 100, 32);
    button1->Click += gcnew System::EventHandler(this, &MyForm::OnClick1);

    button2 = gcnew Button();
    button2->Text = "Button 2 (add 5)";
    button2->SetBounds(10, 50, 100, 32);
    button2->Click += gcnew System::EventHandler(this, &MyForm::OnClick2);

    label = gcnew Label();
    label->Text = "Result area";
    label->SetBounds(10, 90, 200, 32);

    Controls->Add(button1);
    Controls->Add(button2);
    Controls->Add(label);
}

// Click handler for button1, this will add 1 to the member variable result
void MyForm::OnClick1(System::Object ^sender, System::EventArgs ^e) {
    result += 1;
    label->Text = String::Format("Pressed 1, result is {0}", result);
}

// Click handler for button2, this will add 5 to the member variable result
void MyForm::OnClick2(System::Object ^sender, System::EventArgs ^e) {
    result += 5;
    label->Text = String::Format("Pressed 2, result is {0}", result);
}

int main(array<System::String ^> ^args) {
    MyForm^ form = gcnew MyForm();
    Application::Run(form);
    return 0;
}

The MyForm class holds variables for the buttons, but also a result variable that is shared by every method in the class. Thus, when button 1 or 2 modifies the value, the click-handler for the other button can always read it.

Hope this helps,
Fredrik