Question

My problem is that when the action UpdateRect calls the drawRect method, my rect doesn’t update the height!

When I click on the button, I expect to see my rect height to 20 but it remains to 10. Why?

@implementation Graphic_view

int height = 10; //The height of my rect.

-(IBAction)updateRect:(id)sender {
    height += 10;
    //Calling the drawrect method
    [self performSelector:@selector(drawRect:)];
}

-(void)drawRect:(NSRect)dirtyRect {
    NSLog(@"DrawRect has been called !");
    // Drawing code here.
    NSRect viewBounds = [self bounds];
    NSColor *color = [NSColor orangeColor];
    [colore set];
    NSRectFill(viewBounds);
    NSRect myRect;
    myRect.origin.x = 20;
    myRect.origin.y = 20;
    myRect.size.height = height;
    myRect.size.width = 100;
    NSColor *whiteColor = [NSColor whiteColor];
    [whiteColor set];
    NSRectFill(myRect);
} 

@end

Answer 1

You should never call drawRect: yourself. Instead call setNeedsDisplay:

-(IBAction)updateRect:(id)sender {
    height += 10;
    // Schedule the drawrect method
    [self setNeedsDisplay:YES];
}

Note: The iOS equivalent is setNeedsDisplay without an argument.