[MacRuby-devel] My class's initialize not called

steve ross cwdinfo at gmail.com
Thu Jan 21 22:44:06 PST 2010


Thanks for the great explanation. I'm going to have to rethink how my object achieves a known initial state.


On Jan 21, 2010, at 6:41 PM, Brian Chapados wrote:
> Hi Steve (et al),
> So, there are a couple things going on here.  Cocoa classes use the
> concept of a "designated initializer" method, which is a name for the
> instance method that calls the initializer method of the superclass.
> This chain continues until you hit [NSObject#init]. To figure this out
> from the documentation:
> - If a class does not document an initializer method, check the
> superclass, and continue up the chain until you find it.
> - If there are multiple initializer methods, the documentation for
> Cocoa classes will always tell you which method is the designated
> initializer.
> In ObjC/Cocoa:
> If you have a subclass that requires input during initialization, you
> should create a new designated initializer.  That method should call
> the designated initializer of the superclass and you should override
> -init to call your new designated initializer.
> All of this stuff is explained pretty well in Apple's Objective-C guide.
> In Matt's example, he creates a few initialization helper methods, but
> -init is still the designated initializer.
> In your case, NSTextField is a subclass of NSControl, and the
> designated initializer is (from NSControl):
> -initWithFrame:(NSRect)frameRect
> I think your subclass of NSTextField should have an -initWithFrame:
> method or another init method that calls super.initWithFrame:
> Although, if you're not supposed to call super.init in MacRuby, then
> I'm not sure how this is supposed to work.
> Last point: The one odd exception case to the initialization chain is
> the one you hit: NIB files!
> nib/xib files are basically freeze-dried collections of objects that
> are archived into a file.  When they are restored, this is done by
> unarchiving the file, which uses the NSCoder methods. Most of the time
> if you need to do custom configuration on an object instantiated from
> a nib file, you should probably do that in -awakeFromNib.  However, if
> for some reason you really need to do something during object
> initialization, you need to do that in initWithCoder:, since this
> method will be called for objects in a nib file.
> Brian
> On Thu, Jan 21, 2010 at 4:33 PM, steve ross <cwdinfo at gmail.com> wrote:
>> So that confirms my suspicion. It's not so much a MacRuby thing as a Cocoa
>> thing. I just don't see how to set an initial state in a class that's
>> instantiated when a nib is loaded. I don't do the alloc.initWithWhatever. On
>> the previous subject though, adding super/self does not cause the initialize
>> method to be called. Hmmmmmm...
>> On Jan 21, 2010, at 4:20 PM, Matt Aimonetti wrote:
>> Overwriting the init method of a Cocoa class subclass is not recommended.
>> Here is an example of what I was suggesting:
>> http://github.com/mattetti/phileas_frog/blob/master/image_layer.rb#L44
>> Which then get called
>> there: http://github.com/mattetti/phileas_frog/blob/master/game_controller.rb#L57
>> In any cases, you still need to call init (or super if you overwrite
>> initialize) and you need to return self.

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