init is being called and I don't know why?

Question

I am working on the iTuneU Stanford iPhone course HelloPoly drawing assignment, and I am getting a call to my object's init routine when I don't expect one. The callback seem to indicate that the call is coming from _loadMainNibFile (after other calls). What I am trying to understand is why is my object being init-ed implicitly. The source files can be found here: -- http://www.cavedrawings.com/hp2_files.zip

Can anyone tell me why the init routine would be called implicitly when loading the NIB file?

Answer 1

Most implementations of initWithCoder: ultimately call another initialization function. It's normal to stack initialization methods when you have a series of them that progressively add information to the initialization process.

_loadMainNibFile calls the initWithCoder: of the file owner of the nib which in turn calls another initialization method which leads up to the final init.

Answer 2

When a nib is loaded all objects within it get instantiated to do any prep work they need to do.

If you want a nib's object loaded and init'd later, put the object in a separate nib and explicitly load that nib when you need it.

Answer 3

@TechZen: you wrote “most implementations of initWithCoder: ultimately call another initialization function. It’s normal to stack initialzation methods …”

Maybe you didn’t miss it, but for safety: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocAllocInit.html#//apple_ref/doc/uid/TP30001163-CH22-SW14

The third point is the big one in this context: “In the implementation of a custom initializer, you must ultimately invoke a designated initializer.” — Notify the imperative mood!

Greetings

Answer 4

@TechZen: “That's what I said”? You wrote most inits do. This sounds a bit like “if you prefer something else, just do it your way”. No good idea, as your application will do so too. It will start to init and it will never stop it. Not in every case. Maybe just once for a long time as the problem might sit in a rearely used initiator. Then the user will have fun, watching a game of init-pong: http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocAllocInit.html#//apple_ref/doc/uid/TP30001163-CH22-106471

Greetings