dcsimg
CodeGuru Home VC++ / MFC / C++ .NET / C# Visual Basic VB Forums Developer.com
Results 1 to 4 of 4

Thread: change class object

  1. #1
    Join Date
    Nov 2005
    Posts
    102

    change class object

    Suppose i have the following classes:
    Code:
    class testA
    {
    public int myVar = 12;
    }
    
    class testB
    {
    public testA m_testa;
    
    public testB ( testA testa )
    {
        this.m_testa = testa
    }
    }
    And my main class
    Code:
    class Main
    {
    
    public void blaat()
    {
        testA testa = new testA();
        testB testb = new testB(testa);
    
        testa.myVar = 400;
    }
    }
    So as you can see i create an instance of classA in my Main class and pass that to classB.
    What happends when i directly change a value of classA from my Main class and after that display that same value from classB..??

    Will the instance of classA that is in classB also know about that change or will that one still hold the old value??

    If that's the case, how can i make it so that when i change a value of classA from Main that the instance of classA in classB will be exactly the same??

  2. #2
    Join Date
    Mar 2010
    Location
    Mexico
    Posts
    9

    Re: change class object

    Good day

    Code:
    testA testa = new testA();
    testB testb = new testB(testa);
    
    testa.myVar = 400;
    
    // here testa.myVar == testb. m_testa.myVar
    
    // if you want to change testa
    
    testa = new testA()
    
    // you have this: testb.m_testa != testa because tesb has the old reference of testa until you change it manually
    
    testb. m_testa = testa;
    
    // and the old reference testb. m_testa will be garbage collected :)
    I hope this is what you were asking for.

    Thanks

  3. #3
    Join Date
    Sep 2008
    Location
    Netherlands
    Posts
    865

    Re: change class object

    Quote Originally Posted by vivendi View Post
    Will the instance of classA that is in classB also know about that change or will that one still hold the old value??
    Just use the debugger and see for yourself.

  4. #4
    Join Date
    Apr 2002
    Location
    Egypt
    Posts
    2,210

    Re: change class object

    Quote Originally Posted by vivendi View Post
    What happends when i directly change a value of classA from my Main class and after that display that same value from classB..??
    If you mean changing the value of classA changing a value of one of its properties, then yes, the new value will reflect in classB instance. That because classA is a reference type. So both references to classA instance in main and classB are pointing to the same object.
    If you mean changing the object itself (testa = new testA();) this will make testa in main points to a new object other than the one in B.
    Hesham A. Amin
    My blog , Articles


    <a rel=https://twitter.com/HeshamAmin" border="0" /> @HeshamAmin

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Windows Mobile Development Center


Click Here to Expand Forum to Full Width




On-Demand Webinars (sponsored)