View becomes black when I add subview - ios

Question

I'm making app with Quartz 2D drawing. I created a two files: Draw2D.m and Draw2D.h. Then I created button in my View Controller. I created a code to this button. But my view displays only black screen. Here is my code:
ViewController.m
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
#import "Draw2D.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (IBAction)Start {
CGFloat hue = ( arc4random() % 256 / 256.0 ); // от 0.0 до 1.0
CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5; // от 0.5 до 1.0, от белого
CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5; // от 0.5 до 1.0, от черного
self.view.backgroundColor = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
Draw2D *draw2DView = [[Draw2D alloc] initWithFrame:(self.view.bounds)];
[self.view addSubview:draw2DView];
}
Draw2D.m
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 4.0);
CGContextSetStrokeColorWithColor(context,
[UIColor blueColor].CGColor);
CGRect rectangle = CGRectMake(60,170,200,80);
CGContextAddRect(context, rectangle);
CGContextStrokePath(context);
}
Please notice that Draw2D don't have connection with ViewController. And my drawRect don't do nothing, it draw a square. My code should draw blue square on the random background.