On Jun 2, 2016, at 12:26 , Daryle Walker <dary...@mac.com> wrote:
> 
> The NSDocument file handler methods are passed a UTI string of the file's 
> (supposed) type. What error are you supposed to throw when you get an 
> unrecognized UTI?  Or can you punt up to super for that default handling?

You don’t say which methods you mean. (Depending on context, “handler” could 
mean NSDocument action method, NSDocumentController method, some delegate, file 
coordinator, etc.)

You should not get any file type except those you put in your document file 
types in your info.plist. So, you could force a crash if you get something 
unrecognized, or (in the simple case of having only a single document type) you 
can just ignore the type completely.

In Obj-C I used to be religious about checking this sort of thing early and 
often, because the dynamism could sometimes propagate incorrect behavior a long 
way. In Swift, because of the stricter type checking, unexpected values tend to 
blow up much earlier, so I’ve stopped bothering to put in explicit checks for 
things that are just going to explode naturally. (The price you pay is that 
such things are poorly reported when they occur, but OTOH they are never 
supposed to occur.)


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