Question

My code is working so far but I had to create a Class for the UIView. This is a bit inconvenient because I need to interact with the ViewController too.

BTW, I did try [self setNeedsDisplay] on the ViewDidLoad of the UIViewController subclass file but it didn’t work.

Here’s the code, which works on UIView Subclass but doesn’t get called on a UIViewController one:

- (void)drawRect:(CGRect)rect
{
    UIColor *currentColor = [UIColor redColor];

    CGContextRef context = UIGraphicsGetCurrentContext();

    someNum = 1;
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 30, 40);
    [self addDotImageX:30 andY:40];

    CGContextSetLineWidth(context, 2);
    CGContextSetStrokeColorWithColor(context, currentColor.CGColor);
    CGContextStrokePath(context);
}

Any ideas on what to try? BTW, this is a TabBar App. I know those can somehow block the calls to drawRect.

The Tabs where created programatically, not through a Nib. Eg:

NSMutableArray *listOfViewControllers = [[NSMutableArray alloc] init];
UIViewController *vc;

vc = [[Education alloc] init];
vc.title = @"Education";
[listOfViewControllers addObject:vc];
vc.tabBarItem.image = [UIImage imageNamed:@"info.png"];
[vc release];

I would appreciate any ideas. I’ve been through the answers on this site related to setNeedsDisplay not calling drawRect and haven’t found an answer for my particular case.

Thanks.

Answer 1

You are mixing up two classes. A UIViewController is not a UIView, meaning it doesn’t inherits from UIView. But the good news is it has a view, declared as property: It’s composition. The drawRect method is only available in a UIView class/subclass.

If you like to force the controller’s view to redraw you can call

[self.view setNeedsDisplay];

in the viewController.

You can set your own custom view as the view of your viewController with the loadView method. It could look like this:

- (void)loadView
{  
    MySubclassOfUIView *rootView = [[MySubclassOfUIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    // do more view configuration ...

    self.view = rootView;
    [rootView release];
}

So you can keep your drawing code separated in your MySubclassOFUIView.m file.

About the UIViewController:

The UIViewController class provides
the fundamental view-management model
for iPhone applications. The basic
view controller class supports the
presentation of an associated view,
support for managing modal views, and
support for rotating views in response
to device orientation changes.

And the purpose of a UIView:

The UIView class defines a rectangular
area on the screen and the interfaces
for managing the content in that area.
At runtime, a view object handles the
rendering of any content in its area
and also handles any interactions with
that content.

Have a look at Cocoa Core Competencies / Model-View-Controller in Apple’s official documentation, it describes the MVC design pattern.