Class Instantiation

This is a discussion on Class Instantiation within the C++ Programming forums, part of the General Programming Boards category; Hope someone can help me. I need to create a user specified number of differntly named instances of a object, ...

  1. #1
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    Question Class Instantiation

    Hope someone can help me.

    I need to create a user specified number of differntly named instances of a object, in a loop for example.


    Just in case I havent explained clearly:

    User inputs the number of boxes they want
    program then creates this number of boxes from the class Container

    Container box1();
    container box2();

    and then some of the boxes get stuff added to them.
    however since i dont know how many boxes are going to be created, i must have a loop that creates each box, named similarly as above for as many boxes as the user requires.

  2. #2
    Confused Magos's Avatar
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    Use either:

    1) A linked list of dynamically allocated objects.
    2) Since 1) is a pretty advanced topic, you can make a dynamic array containing the objects, something like this:
    Code:
    //Create a pointer
    Container* ConPtr;
    
    ...User input
    
    //Allocate memory
    ConPtr = new Container[NrOfObjects];
    
    //Check if the allocation was successful
    if(ConPtr != NULL)
    {
       for(int i=0; i<NrOfObjects; i++)
       {
          //Since the constructor doesn't work on dynamically allocated
          //objects, you have to run a similar function on them
          ConPtr[i].SetInitialvalues();
       }
    
       ...Do whatever you want
    
       //Deallocate the allocated memory
       delete[] ConPtr;
    }
    MagosX.com

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  3. #3
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    As for the initial question: You can't create variable names after the program is compiled. In fact, once your program is compiled, function names no longer even exist. Remember, C++ isn't an interpreter language, so once it's compiled, the code (and variable names are part of the code) can no longer change. You'll just have to make an array of the things.

    Also, I have a question for Magos:
    //Since the constructor doesn't work on dynamically allocated
    //objects, you have to run a similar function on them
    Hm? Do you mean that if I code

    class Aclass{Aclass(); ~Aclass();};
    Aclass *aclass;
    aclass=new Aclass;

    the constructor is NOT called? Weird! So when ís the constructor called?

  4. #4
    Confused Magos's Avatar
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    Sorry, my fault.
    The constructor is actually called even in dynamic allocations (Made some tests on this one).
    MagosX.com

    Give a man a fish and you feed him for a day.
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