[MacRuby-devel] Create new Core Data Instances

[Sven A. Schmidt]

Hi Timo,

> a) Is it really THAT complicated to create an instance of MyEntity and set the attribute? I'm coming from the Rails/ActiveRecord world where this could easily be done with a single line of code (including saving the instantiated object): MyEntity.new(:attribute1 => "Test").save )
> 
> b) How can I save this fresh instance and update my NSTableView?

After you have modeled your entity in the Xcode core data modeling view, you can use

    instance = NSEntityDescription.insertNewObjectForEntityForName(
      "MyEntity", inManagedObjectContext:managedObjectContext
    )

to instantiate an instance. You can save it calling

    error = Pointer.new_with_type("@")
    managedObjectContext.save(error)

To save attributes, simply assign to them:

    instance.attribute1 = 'Test'

This assumes you've added that attribute to your model. The managedObjectContext can be created or, if you're using a core data project like the document one, you'll have a managedObjectContext accessible from your NSDocument subclass: self. managedObjectContext

If you have bound your NSTableView to the model object, changes will be picked up automatically. You'll only need to call save to actually persist to disk.

I hope this helps somewhat, there's much more detail to it and the following links explain more of those:

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/cdProgrammingGuide.html

and some MacRuby specific ones that I've found useful in the past

http://www.springenwerk.com/2008/10/macruby-and-core-data-tutorial.html
http://cyberfox.com/blog/120-how-i-learned-to-stop-worrying-about-core-data-and-love-macruby
http://reborg.tumblr.com/post/263347770/macruby-coredata-tutorial

Cheers,
Sven

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