Question

Is there a method that is always called in Cocoa? Many classes have init or initWith, but even worse they can be loaded from a nib or something. I don’t want to have to scrape around and find how it does this in this case. I just want to set some initial variables and other things, and I want a method to subclass that I can depend on no matter if it’s a UIView, UIViewController or UITableViewCell etc.

Answer 1

No there is not such a method. init comes from NSObject so every object can use it, and as well subclasses define their own initialization methods. UIView, for example, defines initWithFrame: and furthermore there are init methods from protocols, such as NSCoding which defines initWithCoder:. This is the dynamic nature of objective-C, anything can be extended at any time. That being said, there are some patterns. UIViewController almost always takes initWithNibName:bundle: and UIView almost always takes initWithFrame: or initWithCoder:. What I do is make an internal initialize method, and just have the other inits call it.

- (void)initialize
{
    //Do stuff
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if(self)
    {
        [self initialize];
    }
}

- (id)initWithCoder:(NSCoder *)aCoder
{
    self = [super initWithCoder:aCoder];
    if(self)
    {
        [self initialize];
    }
}