On 27/07/2009, at 2:09 PM, Quincey Morris wrote:
On Jul 26, 2009, at 20:39, David Blanton wrote:
I have 22 file types, each with its own C++ methods for extracting
its data.
Now, I could use just one subclass of NSDocument and in the
- (BOOL)readFromData:(NSData *)data ofType:(NSString *)typeName
error:(NSError **)outError
method do a case statement on typeName BUT I think it would be
cleaner to subclass NSDocument for each of my file types and
override only the read and write methods.
If the *only* reason for making separate subclasses is the code to
extract the data, I don't see any great advantage. You need 22
pieces of code, and it's probably easier for housekeeping purposes
to keep them all in one place than to spread them around. (But
separate subclasses would be in no way wrong.)
If there are other behavioral differences, then it might make more
sense to use different subclasses.
HTH IMO FWIW
There are many other approaches you could take also.
In my app I have one document class but a simple schema for extending
the types of files it can read and write by mapping file types (and/or
UTIs) to specific method selectors. The mapping table is a simple
dictionary. This allows me to add the method via a category, amend the
mapping table and info.pList and away it goes. The core document class
never changes so I can reuse that code in many different apps.
This is no better or worse in terms of the amount of code you need to
write but it does make managing it quite easy.
--Graham
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