Binding a function argument

This is a discussion on Binding a function argument within the C++ Programming forums, part of the General Programming Boards category; Hi I have a problem with a plugin I am making. The program I am plugin into only allows me ...

  1. #1
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    Jan 2006
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    Binding a function argument

    Hi I have a problem with a plugin I am making. The program I am plugin into only allows me to use functions with no arguments, but I want to use the same function for an unknown(at compile time) number of different callbacks all with different arguments.

    I want different user information to pass to the function when the user initiates the calling of this function, depending on which part of the program called the function. The user information will be stored in a configuration file.

    I hope this is clear enough for people to work out what I mean. In essence I can try and put it as this pseudo code:

    Code:
    void func (char *arg) { 
        /*...do stuff...*/
    }
    
    void newfunc() = bind(&oldfunc, arg)

  2. #2
    Code Goddess Prelude's Avatar
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    9,796
    >I hope this is clear enough for people to work out what I mean.
    Not really, but I get the feeling that a function object would be better suited to what you're trying to accomplish. You can also get a variable number of callbacks with a collection of handles (but please don't use varargs).
    My best code is written with the delete key.

  3. #3
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    I dont know exactly what you mean, but can't you just use the functions with no arguments and use a global variable as paramater info?

    Code:
    name = "itsme";
    
    void func()
    {
      cout << name << endl;
    }

  4. #4
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    Unfortuanatly function objects wouldn't work as the program I'm plugin into won't accept them (it crashes). Maybe I should try to explain with some example code.

    Example of my code
    Code:
    void func(char *text) {
      cout << text << endl;
    }
    
    functions funcArray[3];
    funcArray[0] = func;
    funcArray[1] = func;
    funcArray[2] = func;
    
    functions getFuncs ()
    {
      return funcArray;
    }
    Example of the other programs code
    Code:
    /* When user clicks on a menu item */
      callable = getFuncs()[itemID];
      callable();
    Obviously the above wouldn't work as no argument is being given to func. I can't tell which menu item triggered the function being called so I can't set a global variable.
    Last edited by nectodn; 11-20-2006 at 01:58 PM.

  5. #5
    CSharpener vart's Avatar
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    Rishon LeZion, Israel
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    Code:
    void func(char *text) {
      cout << text << endl;
    }
     
    void func0(void)
    {
       func("text0");
    }
    void func1(void)
    {
       func("text1");
    }
    void func2(void)
    {
       func("text2");
    }
    functions funcArray[3];
    funcArray[0] = func0;
    funcArray[1] = func1;
    funcArray[2] = func2;
     
    functions getFuncs ()
    {
      return funcArray;
    }
    /* When user clicks on a menu item */
      funcArray[itemID]();
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  6. #6
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    My problem is that the exact text will not be known at compile time. The text will be gleaned from a file once the program is running and is subject to change. I will not even know how many functions I will use until run-time.

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