Re: Can a value transformer get its own registration name?
Re: Can a value transformer get its own registration name?
- Subject: Re: Can a value transformer get its own registration name?
- From: Bill Cheeseman <email@hidden>
- Date: Thu, 12 Apr 2007 14:33:54 -0400
- Thread-topic: Can a value transformer get its own registration name?
on 2007-04-12 1:58 PM, Jim Correia at email@hidden wrote:
> On Apr 12, 2007, at 1:33 PM, Bill Cheeseman wrote:
>
>> Of course I could do the same thing with multiple transformer
>> subclasses or,
>> as you pointed out, with a single subclass with a registered name
>> iVar to
>> use in the if-else chain. To my mind, the "generalized" subclass
>> approach
>> based on registered names and pointer comparisons is simpler to
>> implement,
>> both because I only need to write one subclass and I don't need to
>> mess with
>> iVars, -initWith... methods and all that. I just use the
>> registration naming
>> facility that NSValueTransformer already provides.
>
> That's where we disagree. You only have to write one subclass. It it
> just a matter of how you tell the instance how to do its work.
>
> It is much easier, and straight forward, for an instance to have
> those parameters directly available via iVars.
>
> Trying to encode these in the registration name is not the way to go,
> IMO. Especially given the considerations previously posted.
What I'm not getting is how you actually use a value transformer instance in
your scenario, if you don't rely on the registration name to distinguish
between instances having different behavior. The value transformer field in
the view binding pane in the IB inspector requires a registration name.
Or are you saying that you do rely on the registration name, but only to get
the right instance -- and that the instance's behavior is then determined by
the iVar you embedded in it when it was initialized?
I concede that using an iVar in this way makes for more understandable and
maintainable code, since a reader will see the importance and role of the
ivar at first glance rather than having to find it isolated in the
-transformedValue: method. It's probably also easier to adjust as you work
on an app-in-development.
--
Bill Cheeseman
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