public accesor function

This is a discussion on public accesor function within the C++ Programming forums, part of the General Programming Boards category; Hello, I've run the following: Code: #include <iostream> using namespace std; class Rectangle { private: int x, y, w, h; ...

  1. #1
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    Nov 2008
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    public accesor function

    Hello,

    I've run the following:
    Code:
    #include <iostream>
    
    using namespace std;
    
    class Rectangle
    {
    	private:
    	int x, y, w, h;
    	
    	public:
    	Rectangle();
    	int get_width() {return w;}
    	int get_height() {return h;}
    };
    
    class Area
    {
    	private:
    	int area;
    	
    	public:
    	Area();
    	int get_area();
    };
    
    Area::Area()
    {
    	area = 0;
    }
    
    int Area::get_area()
    {
    	area = myRectangle.get_width() * myRectangle.get_height();
    	return area;
    }
    
    Rectangle::Rectangle()
    {
    	x = 0;
    	y = 0;
    	w = 10;
    	h = 20;
    }
    
    int main()
    {
    	Rectangle myRectangle;
    	Area myArea();
    	
    	
    	cout << myArea.get_area() << endl;
    	cout << myRectangle.get_width() << endl;
    
    	return 0;
    }
    I get the following errors:
    Code:
    class5.cpp: In member function ‘int Area::get_area()’:
    class5.cpp:33: error: ‘myRectangle’ was not declared in this scope
    class5.cpp: In function ‘int main()’:
    class5.cpp:51: error: request for member ‘get_area’ in ‘myArea’, which is of non-class type ‘Area ()()’
    How do I access the get_width() and get_height() functions in get_area()? Since they are public in Rectangle, shouldn't I be able to access them in Area? If I comment out the two lines giving me issues, I can access myRectangle.get_width() from main. I don't understand why I can access get_width() in main but not in get_area().

  2. #2
    C++ Witch laserlight's Avatar
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    Singapore
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    Quote Originally Posted by swappo
    Since they are public in Rectangle, shouldn't I be able to access them in Area?
    Yes, if you had a Rectangle to access them with. Unfortunately, you don't, since the Area class does not have any Rectangle related member variable and its get_area() member function does not have any parameters related to Rectangle.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Making mistakes
    Join Date
    Dec 2008
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    The C++ Compiler looks only at local and global variables. MyRectangle is neither for get_area. It's declared in another function, main. You can't access variables declared in a calling function (except passing them as an argument).

  4. #4
    Registered User
    Join Date
    Nov 2008
    Posts
    56
    I tried putting an argument in the get_area function.
    Code:
    #include <iostream>
    
    using namespace std;
    
    class Rectangle
    {
    	private:
    	int x, y, w, h;
    	
    	public:
    	Rectangle();
    	int get_width() {return w;}
    	int get_height() {return h;}
    };
    
    class Area
    {
    	private:
    	int area;
    	
    	public:
    	Area();
    	int get_area(Rectangle *myRectangle);
    };
    
    Area::Area()
    {
    	area = 0;
    }
    
    int Area::get_area(Rectangle *myRectangle)
    {
    	area = myRectangle->get_width() * myRectangle->get_height();
    	return area;
    }
    
    Rectangle::Rectangle()
    {
    	x = 0;
    	y = 0;
    	w = 10;
    	h = 20;
    }
    
    int main()
    {
    	Rectangle myRectangle;
    	Area myArea();
    	
    	
    	cout << myArea->get_area(&myRectangle) << endl;
    	cout << myRectangle.get_width() << endl;
    
    	return 0;
    }
    I got the following error.
    Code:
    class5.cpp: In function ‘int main()’:
    class5.cpp:51: error: request for member ‘get_area’ in ‘myArea’, which is of non-class type ‘Area ()()’
    I am not sure whether to pass the class to get_area() or to pass get_width() and get_height().

  5. #5
    The larch
    Join Date
    May 2006
    Posts
    3,573
    Code:
    Area myArea;
    Otherwise myArea is a function declaration.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

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