How to do a lightweight Core Data migration

Why do you need to migrate?

When you release an app and add new features, there will be a time you need to update you persistent store. This is easy to do when you are in a development stage, because you can just delete your app and the persistent store will be re-generated. But when you are live and people have downloaded your app, you need to be careful. They won’t like it if suddenly their saved data has disappeared!

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iOS Face recognition

There is a nice API for face/person recognition on the internet at http://www.face.com/.
Their API provides quite a lot of interesting data, such as

  • Position of the eyes
  • Position of the nose
  • Position of the mouth (right, center, left bounds)
  • Yaw/roll/pitch rotation of the detected head
  • Attributes: gender, wearing glasses, smiling, mood, …

And the best of all … it’s a free service which gives you 5000 calls an hour to their API which is more than enough for a little experiment.

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