iphone - Programmatically creating Views in IOS (how does it work)?

Question

A little background: I'm going through the CS193P iTune videos and I was stuck on the assignment 3 for the longest time. Basically, the assignment asks you to programmatically create a custom view to display a shape on the screen. I'm not using any view controllers by the way.

I could not get my view to display until I finally dragged a View object in Interface Builder and change the object name to my custom view class. So my question is when people say to programmatically create a view, are they just saying manually create the class but when you need to display it use IB? I can't help feeling like I misunderstood something?

edit: let me be more clear. My custom view has been initialized with a frame of 0, 0, 200, 150 and drawRect is overriden to draw a square in it. My view doesn't even show up if try adding it to the main window within my controller:

    UIWindow* window = [UIApplication sharedApplication].keyWindow;
[window addSubview:polygonView];

However, if use drag a view in IB and change the class to my view class, it shows up fine.

Edit: Added some code. This is my controller's awakeFromNib method where the view should be drawn.

    - (void)awakeFromNib {
    shape = [[PolygonShape alloc] initWithNumberOfSides:numberOfSidesLable.text.integerValue minimumNumberOfSides:3 maximumNumberOfSides:12];
    polygonView = [[PolygonView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    polygonView.backgroundColor = [UIColor blackColor];
    [window addSubview:polygonView];
    [self updateInterface];  
}

Part of my controller's updateInterface method:

- (void)updateInterface {
    [polygonView setPolygon:shape];
    [polygonView setNeedsDisplay];
...
}

PolygonView.h

#import <UIKit/UIKit.h>
#import "PolygonShape.h"

@interface PolygonView : UIView {
    IBOutlet PolygonShape *polygon; 
}

@property (readwrite, assign) PolygonShape *polygon;

- (void)drawRect:(CGRect)rect;
@end

PolygonView.m

#import "PolygonView.h"

@implementation PolygonView
@synthesize polygon;

- (id)initWithFrame:(CGRect)frame {

    self = [super initWithFrame:frame];
    if (self) {
        nslog(@"initialized");
    }
    return self;
}

- (void)drawRect:(CGRect)rect {
       CGRect bounds = [self bounds];

    [[UIColor grayColor] set];
    UIRectFill(bounds);

    CGRect square = CGRectMake(10, 10, 10, 100);
    [[UIColor blackColor] set];
    UIRectFill(square);

    [[UIColor redColor] set];
    UIRectFill(square);
    NSLog(@"drawRect called");
}
@end

The polygonView is being initialized but the drawRect isn't being called.

Answer 1

To be even more specific to your question, the syntax would be

UIWindow* window = [UIApplication sharedApplication].keyWindow;

UIView *polygonView = [[UIView alloc] initWithFrame: CGRectMake ( 0, 0, 200, 150)];
//add code to customize, e.g. polygonView.backgroundColor = [UIColor blackColor];

[window addSubview:polygonView];
[polygonView release];

This is a pattern you will use for not only this but subviews afterwards. Also, another note is with many of the templates, the viewController is already set up with it's own view. When you want to make a custom view, you create it like above but instead of the method above you set the viewControllers view to the newly created view like so:

viewController.view = polygonView;

Good luck!