iOS [SOLVED] Why am I able to send "drawInRect" to an NSString object?

//Add some text
    NSString *text = @"You are getting sleepy.";
    
    //Get a font to draw it in
    UIFont *font = [UIFont boldSystemFontOfSize:28];
    
    //Where am I going to draw it?
    CGRect textRect;
    [B]textRect.size = [text sizeWithFont:font]; //Confusion here[/B]
    textRect.origin.x = center.x - textRect.size.width  * 0.5;
    textRect.origin.y = center.y - textRect.size.height * 0.5;
    
    //Set the fill color of the current context to black
    [[UIColor blackColor] setFill];
    
    //Set the shadow to be offset 4 points right, 3 points down
    //and dark grey with a blur radius of 2 points
    CGSize offset = CGSizeMake(4, 3);
    CGColorRef color = [[UIColor darkGrayColor] CGColor];
    CGContextSetShadowWithColor(context, offset, 2.0, color);
    
    //Draw the string
   [B] [text drawInRect:textRect withFont:font]; //Confusion here[/B]
}