How do I use Core Data with the Cocoa Text Input system?

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Hobbyist Cocoa programmer here. Have been looking around all the usual places, but this seems relatively under-explained:

  • I am writing something a little out of the ordinary. It is much simpler than, but similar to, a desktop publishing app. I want editable text boxes on a canvas, arbitrarily placed.

  • This is document-based and I’d really like to use Core Data.

Now, The cocoa text-handling system seems to deal with a four-class structure: NSTextStorage, NSLayoutManager, NSTextContainer and finally NSTextView. I have looked into these and know how to use them, sort of. Have been making some prototypes and it works for simple apps.

The problem arrives when I get into persistency. I don't know how to, by way of Cocoa Bindings or something else, store the contents of NSTextStorage (= the actual text) in my managed object context.

I have considered overriding methods pairs like -words, -setWords: in these objects. This would let me link the words to a String, which I know how to store in Core Data. However, I’d have to override any method that affects the text - and that seems a little much.

Thankful for any insights.

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objective-ccocoacore-datamacosnstextview

2 Answers

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NSTextStorage is just a subclass of NSMutableAtrributedString which support the NSCoding protocol so you can save it in Core Data as a transformable attribute using the default NSKeyedUnArchiveFromData transform.

I'm pretty sure that holds true for all the other classes you might want to save with the possible exception of the views. (I've never tried to store them in Core Data buts its theoretically possible to do so.)

Any class that implements/inherits NSCoding or has a initWithCoder: method can be stored in code data as a transformable attribute.

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I suggest binding the value binding of a text view to a string attribute of one of your model entities, or the attributedString binding to a transformable attribute. This hooks up the view to the model without you having to pass text back and forth yourself.