Re: Clarification regarding viewDidAppear: and friends
Re: Clarification regarding viewDidAppear: and friends
- Subject: Re: Clarification regarding viewDidAppear: and friends
- From: WT <email@hidden>
- Date: Sat, 28 Mar 2009 22:12:56 +0100
Hi Hank,
thanks for your quick reply.
On Mar 28, 2009, at 9:56 PM, Hank Heijink (Mailinglists) wrote:
1) If the default implementation does nothing, why must I invoke
super when overriding this method?
You're right, that's confusing. Could be several answers though:
maybe super does nothing visible, but still something; or maybe
super could start doing something in the future. It's better to be
prepared, but without more info from Apple, it's hard to say.
That's what I thought too, but "nothing" is quite specific a word and
I didn't think that it would be used so cavalierly in the documentation.
2) viewDidAppear: and its friends all take a boolean argument but I
don't understand what it's for. In the case of viewDidAppear:, for
instance, the view has already been fully displayed, so what
animations is the description above talking about? Note, for
instance, that the description explicitly says
"Sent to the controller after the view fully appears and animations
end."
So, again, if the animations have ended, what's the boolean
argument for?
Suppose you do all sorts of stuff when animated is YES and you set
it all up in viewWillAppear:. The place to clean up all that stuff
would be viewDidAppear:. The boolean is there so you can coordinate
the behavior with viewWillAppear:.
Ah, ok. That makes perfect sense now.
3) The documentation for each of those methods says:
"Subclasses may override this method to take an appropriate action.
When doing so, they must invoke super."
Now, should I invoke super before or after my custom code?
That would depend on what your code does and what super does. If
super doesn't do anything (like the docs say) it shouldn't matter.
Naturally. The real question I was asking was if anyone knew that it
should be one way or another because of some other piece of
documentation that I might have missed.
Generally, I like to nest things, so in viewWillAppear I will put my
custom code first and then invoke super, and in viewDidAppear I'd
invoke super first and then have my custom code.
Or the other way around (super first in viewWillAppear and super last
in viewDidAppear). :)
Nesting has also been my policy when dealing with any paired set of
methods like these.
I will send a documentation enhancement request, but I thought I'd
check with the list first to make sure I'm not missing something
obvious.
I'd file the request.
I'm on it.
Thanks again for answering.
Wagner
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