NSValueTransformer and context question
NSValueTransformer and context question
- Subject: NSValueTransformer and context question
- From: Ken Victor <email@hidden>
- Date: Sun, 4 Dec 2005 13:37:04 -0800
my environment:
multi doc, multi window core data app
several windows have an NSTableView bound to an NSArrayController
the NSArrayController gets it managedObjectContext from the file's
owner (in the nib file) which is my subclass of NSPersistantDocument
what i'd like to do:
for some columns, i'd like to be able to use a subclass of
NSValueTransformer to transform a value (an int) from my db into a
date. the transformation requires access to the "owning" document.
what i tried:
in my nib file, i instantiated MyValueTransformer
MyValueTransformer has an outlet connected to the file's owner
in [MyValueTransformer awakeFromNib] i called [NSValueTransformer
setValueTransformer: self forName: @"MyValueTransformer"]
in my nib, i set the value transformer for the appropriate columns to
MyValueTransformer
the results:
this worked fine as long as only one document was open and i didn't
close any windows that took advantage of this setup.
but, if i did close one of those windows, then my transformer
associated with the closed window is deallocated, and since
transformers are accessed via their registered names, things "broke
down" :-)
(actually, i was a little surprised that it worked as well as it did!)
what i've done as a temporary(?) solution:
i've implemented another accessor in my subclass of NSManagedObject
that actually does the transformation i want and bound the column to
this key (instead of to the key for the value in the db). this works
fine... but...
what i'd prefer to do / question
i'd prefer somehow to use a value transformer rather than having this
extra code for my NSManagedObject subclass. is this possible? ie, can
a subclass of NSValueTransformer somehow have a context that is the
document?
thanx,
ken
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