How to specify which NSView to draw on in objective-c?

Question

I found this example of drawing a rectangle in objective-c cocoa

NSRect r = NSMakeRect(10, 10, 50, 60);
NSBezierPath *bp = [NSBezierPath bezierPathWithRect:r];
NSColor *color = [NSColor blueColor];
[color set];
[bp stroke];

However, where should I specify which NSView to draw on in the code?

For example, if I have two NSView objects, and I run this code, how do I specify which one to draw on?

Answer 1

You don't run this code on an NSView , rather it runs in an NSView subclass's override of the -drawRect: method.

You'll need to create your own subclass of NSView , then in that subclass, override -drawRect: and put this code there:

@interface CustomView : NSView
@end

@implementation CustomView

- (void)drawRect:(NSRect)dirtyRect
{
    NSRect r = NSMakeRect(10, 10, 50, 60);
    NSBezierPath *bp = [NSBezierPath bezierPathWithRect:r];
    NSColor *color = [NSColor blueColor];
    [color set];
    [bp stroke];
}

@end

Finally, you will of course have to instantiate an instance of CustomView and add it to your view hierarchy, just as you would normally do with a regular NSView .

Answer 2

子类NSView ，将代码添加到子NSView的drawRect:方法中，然后将适当的NSView替换为NSView的实例。