How to refer an int type

This is a discussion on How to refer an int type within the C# Programming forums, part of the General Programming Boards category; I have one class A which has an "int" field b; I defined another int type variable c. When I ...

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    How to refer an int type

    I have one class A which has an "int" field b; I defined another int type variable c. When I make any changes to A.b, I want c changes accordingly such that c=A.b .

    One can always add a line c=A.b whenever A.b changes. But is there any better way to do that such as the method used in C/C++ : we can let c be a reference of A.b? (eg.: c=&(A.b) in c++)

    thanks

  2. #2
    and the hat of int overfl Salem's Avatar
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    You can, but at that point you should stop pretending that you're using C++.

    Having a pointer (c) which is outside your class, pointing directly at a data member of the class (A.b) flies directly in the face of one of the primary reasons for creating C++ in the first place. Namely that one of the problems of writing larger systems was people forever meddling in an uncontrolled manner in other peoples data.
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    Hi salem, that makes sense. Actually, I don't want to change the value A.b outside A bypassing A's public property or methods. What I want is letting c be a read-only alias of A.b.
    Code:
    public class B
    {
        private List<int> A;
        public int c;
    }
    I want that c always equals to A.Count, thus I can use B.c instead of B.A.c . I am thinking if I have a smart way to avoid adding c=A.Count everywhere in class B because I change A's contents frequently in B. Any ideas?
    Last edited by igoogleu; 09-21-2008 at 10:58 AM.

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    and the hat of int overfl Salem's Avatar
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    What's "frequent" ?
    A million times a second?

    If you write your method as an inline function, the compiler will likely optimise away any call overhead and reading the integer will be a single instruction anyway, without the need to resort to interface-busting trick accesses. This is commonly called "premature optimisation disease".

    First rule is write clear simple code which does what you want.
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    If I'm understanding correctly, I guess you could create an event that gets set in the mutator of class A's b field, subscribe to the event and change c accordingly?

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    Quote Originally Posted by Salem View Post
    What's "frequent" ?
    A million times a second?

    If you write your method as an inline function, the compiler will likely optimise away any call overhead and reading the integer will be a single instruction anyway, without the need to resort to interface-busting trick accesses. This is commonly called "premature optimisation disease".

    First rule is write clear simple code which does what you want.
    well, by "frequent" I mean I will manipulate A in many methods of B now and in the future. Thus each time I write a method manipulating A, I have to add a line "c=A.b". If there is a way I can write just one line which links c to A.b, thus I can access c outside B in a read-only manner, and save some duplicated code lines ("c=A.b") and avoid some trouble in case of forgetting to add c=A.b.

    That has nothing to do with the inline function to save some parameter stacking time.

    Thanks.

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    in your example with List<int>, you can just write a property to return the value of .Count

    i'm still not really clear what you're trying to do though. B sounds like a custom class. but can you explain in more detail with A and c's types are?
    Last edited by bling; 09-21-2008 at 01:30 PM.

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    Quote Originally Posted by igoogleu View Post
    Code:
    public class B
    {
        private List<int> A;
        public int c;
    }
    I don't know what language that is, but is isn't C++.
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    Quote Originally Posted by bling View Post
    in your example with List<int>, you can just write a property to return the value of .Count

    i'm still not really clear what you're trying to do though. B sounds like a custom class. but can you explain in more detail with A and c's types are?
    Currently I wrote a property "c" to return the value of .Count, but I have to add c= .Count everywhere .Count changes, right?

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    Quote Originally Posted by cpjust View Post
    I don't know what language that is, but is isn't C++.
    I don't know what was Mod doing? I posted it in C# section, and I am asking a C# question. Why move it to C++ section?

  11. #11
    Confused Magos's Avatar
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    What you're looking for is called a property. Syntactically it's like using a variable though technically it's still a function (method) call.
    Code:
    public class MyClass
    {
      public int c
      {
        get
        {
          return A.c;
        }
      }
    
      private List<int> A;
    }
    And use it as such:
    Code:
    MyClass m = new MyClass();
    int NrOfItemsInList = m.c;
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    Quote Originally Posted by Magos View Post
    What you're looking for is called a property. Syntactically it's like using a variable though technically it's still a function (method) call.
    Code:
    public class MyClass
    {
      public int c
      {
        get
        {
          return A.c;
        }
      }
    
      private List<int> A;
    }
    And use it as such:
    Code:
    MyClass m = new MyClass();
    int NrOfItemsInList = m.c;
    Thanks! That's what I did last night! I was thinking too much and forgot the simplest way. I don't need a reference to A.c if I just use property like that.

  13. #13
    Confused Magos's Avatar
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    "return A.c" should be "return A.Count", but I guess you figured that out
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