iPhone UIStringDrawing usage

Question

Could someone please explain to me how to draw a string using UIStringDrawing instead of using a label? here is my code but for some reason it compiles and the screen is blank...

//
// MainViewController.m
// DotH
//

#define WINDOW_FRAME [[UIScreen mainScreen] bounds]
#define SCREEN_FRAME [UIScreen mainScreen].applicationFrame
#define GRAY [UIColor grayColor]
#define BLACK [UIColor blackColor]

@implementation MainViewController

- (void)loadView {

  UIView *view = [[UIView alloc] initWithFrame:SCREEN_FRAME];
  [view setBackgroundColor:GRAY];

  [BLACK setFill];

  NSString *string = @"Hey Dude!";
  [string drawAtPoint:CGPointMake(50, 50) withFont:[UIFont systemFontOfSize:14]];

  self.view = view;
  [view release];

}

@end

Answer 1

The line

[string drawAtPoint:CGPointMake(50, 50) withFont:[UIFont systemFontOfSize:14]];

needs to be in the view's drawRect: method.

This is because just before drawRect: is called, the rectangle passed as an argument to drawRect: is erased. So if you try to do custom drawing anywhere other than a view's drawRect: method, the stuff you draw will get erased whenever drawRect: is called. (Not to mention that calling drawAtPoint: is meaningless if not done by code within a UIView.)

You will need to make a custom subclass of UIView, and that subclass will need a custom drawRect: method. If you still want the view controller to be the entity responsible for deciding what string should be drawn and how, you should give your UIView subclass a method like

- (void)addString:(NSString *)string atPoint:(CGPoint)point withFont:(UIFont *)font;

That method can store that information, in, e.g., three NSMutableArrays (one of strings, one of points, and one of fonts), and increment a counter of how many strings have been added. Then, your view's drawRect: method can draw the strings described in those arrays. To add a string, your view controller just calls addString:atPoint:withFont: on your view.