O'kay, that was helpful.
I still have one doubt. The declaration of NSRectFill is as below:
void NSRectFill (
NSRect aRect
);
NSRectFill() is a C function, not part of any class e.g. NSView. aRect is
simply a struct which specify location points (doesnt contain reference of any
window). How the function knows about the drawing surface, in which
window/surface to paint? Does it implicitly make use of some self pointer? If
so, then, what if this function is not called from inside a simple C function
then there will not be any self pointer?
Thank You,
-Vks
Hamish Allan <[EMAIL PROTECTED]> wrote:
Hi Vikas,
On Thu, Jun 12, 2008 at 6:26 PM, Vikas wrote:
> I have recently started programming on Mac using Objective-C and Cocoa. I am
> coming from C++/C# world. So, its a fairly basic question. Please help me
> understand the following code:
>
> @implementation MyView /*MyView inherits from NSView */
> -(void)drawRect: (NSRect)aRect {
> [[NSColor blackColor] set];
> NSRectFill( [self bounds] );
> }
>
> In first line, I was expecting something like [self setColor:[NSColor
> blackColor]]; (similar to this.color = NSColor.blackColor; in C#/C++)
> how NSColor object knows about where to set the color?
It's not setting the color of the NSView, it's setting the color of
the pen used by subsequent drawing operations such as NSRectFill().
> In second line, NSRectFill(), I was expecting it to be called using square
> bracket [] notation. Again how this function knows where to fill the
> rectangle? There is no reference of NSView passed into the function?
The NSView reference is "self", as the code is implementing a method
of an NSView subclass. NSRectFill is a C function, not an Objective-C
method; you can mix C and Objective-C freely in a .m file.
> Lastly what are the rules of using () verses []?
If you want to call a plain C function, use the function name plus
parentheses just as you would in a plain C program. If you want to
call a method on an object, use the square bracket notation [objName
methodSelector].
Hamish
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