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Editorial Team
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Asked: 2026-05-15T09:11:29+00:00

The documentation on Core Data entities says: You might implement a custom class, for

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The documentation on Core Data entities says:

You might implement a custom class,
for example, to provide custom
accessor or validation methods, to use
non-standard attributes, to specify
dependent keys, to calculate derived
values, or to implement any other
custom logic.

I stumbled over the non-standard attributes claim. It’s just a guess: If my attribute is anything other than NSString, NSNumber or NSDate I will want to have a non-standard Attribute with special setter and getter methods? So, for example, if I wanted to store an image, this would be a non-standard Attribute with type NSData and a special method, say -(void)setImageWithFileURL:(NSURL*)url which then pulls the image data from the file, puts in in an NSData and assigns it to core data?

Or did I get that wrong?

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1 Answer

  1. Editorial Team

    A non-standard attribute can be anything. Some common examples are:

    • an image
    • a binary key
    • encrypted data
    • audio

    Just about anything that cannot be represented as a number or string falls into this category.

    update

    Transformable is not a data type of it’s own. It is a way to say that a non-standard value is going to be stored here. Under the covers it is binary. The Transformable tag is a hint to Core Data to go look at the subclass’s property setting.

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