array in structure help

This is a discussion on array in structure help within the C++ Programming forums, part of the General Programming Boards category; I have a structure with an array, but the array size I know only after my program has done something ...

  1. #1
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    array in structure help

    I have a structure with an array, but the array size I know only after my program has done something else which would then set the varSize variable. But how do I do this if the array is in a structure??

    Code:
    struct database
    {
      int anArray[varSize]
    };
    how do I "pass" in varSize so when I make an instance of the structure it creates an array with "varSize" number of elements? I don't wnat to use global variables to keep in practise of good programming

  2. #2
    Senior Member joshdick's Avatar
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    You'll need to use the new operator to allocate memory at runtime. Otherwise, your array size must be a constant known at compile time.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  3. #3
    mustang benny bennyandthejets's Avatar
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    To expand on joshdick's statement, here's some code:

    Code:
    struct database
    {
       int *anArray;
    };
    
    .
    .
    .
    
    int main()
    {
          int size;
    
          cin >> size;
    
          database db;
          db.anArray=new int[size];
    
          //Use the array however you want
    
         delete [] db.anArray;
         return 0;
    }
    benforbes@optusnet.com.au
    Microsoft Visual Studio .NET 2003 Enterprise Architect
    Windows XP Pro

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  4. #4
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    Thanks joshdick and bennyandthejets

    I guess new allocattes memory on the heap and delete frees up resources after

  5. #5
    Senior Member joshdick's Avatar
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    Originally posted by bobnet
    Thanks joshdick and bennyandthejets

    I guess new allocattes memory on the heap and delete frees up resources after
    The Force is strong with this one.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

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