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Re: controlTextDidChange, backspace possible?

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Re: controlTextDidChange, backspace possible?

Subject: Re: controlTextDidChange, backspace possible?
From: "M. Uli Kusterer" <email@hidden>
Date: Tue, 14 Sep 2004 22:54:22 +0200

At 19:24 Uhr +0200 14.09.2004, Ondra Cada wrote:

It does not seem to me to be the GUI task at all to decide how many characters fits there. IMHO, it belongs to the model, or at the very least the controller, level.

I could see arguments for both. On one hand, the view is the place where the user edits stuff, and the user is usually the most reliable source of invalid data. :-) So, the view should take care of converting user interaction into valid data, together with the view controller. Sometimes in MVC the controller is both a view controller and a model controller, sometimes we have these two as separate entities, talking to each other.

I consider NSFormatter to be a view controller, which is why I feel fine letting it do something like that.

I can see how, if you have only one controller, you may decide to say: The controller is the equivalent to the view controller, I'll put the code in there.

Also, if you have many views working on the same model, I could see how you'd want a central bottleneck to take care of validation, so you don't have to set that up for each view separately. In that case, having it in the controller is sensible as well.

However, I can't really decide which one would be better. Personally, since my interpretation of NSFormatter is as a view controller, I'd go with that. But I don't claim to be an MVC guru. I'm still trying to understand some of the grey areas here, and I'd love for someone to provide me arguments that clarify the situation.

I think the formatter would *not* actually limit the number of characters: it would only make sure a validation problem (detected and reported on the proper level) is shown properly in GUI, presumed it is not done all right by the framework code itself (which I am not at the moment sure of and have no time just now to test).

What speaks against such a collaboration, though, is that NSFormatter already exists as a class in AppKit (or actually, in Foundation ...), and already supports performing autonomous validation without involvement from another controller whatsoever. So far, most of AppKit's seeming oddities actually turned out to be cases where I was using it the wrong way. So I'm loathe to think that the way all sample code so far has been using NSFormatter was a violation of MVC and thus the paradigm at the heart of AppKit and Cocoa. -- Cheers, M. Uli Kusterer ------------------------------------------------------------ "The Witnesses of TeachText are everywhere..." http://www.zathras.de _______________________________________________ Do not post admin requests to the list. They will be ignored. Cocoa-dev mailing list (email@hidden) Help/Unsubscribe/Update your Subscription: This email sent to email@hidden References: >controlTextDidChange, backspace possible? (From: "Peter Karlsson" <email@hidden>) >Re: controlTextDidChange, backspace possible? (From: "M. Uli Kusterer" <email@hidden>) >Re: controlTextDidChange, backspace possible? (From: Ondra Cada <email@hidden>) >Re: controlTextDidChange, backspace possible? (From: "M. Uli Kusterer" <email@hidden>) >Re: controlTextDidChange, backspace possible? (From: Ondra Cada <email@hidden>) Prev by Date: Re: controlTextDidChange, backspace possible? Next by Date: Re: autorelease - when is retain count decremented Previous by thread: Re: controlTextDidChange, backspace possible? Next by thread: Re: controlTextDidChange, backspace possible? Index(es): Date Thread