CODEWITHSUNDEEP
ioscore-data
ChickensDontClap
ChickensDontClap

Reputation: 2051

CoreData -to many relationships

I'm beginning to use Core Data and I'm trying to get a solid understanding of how it would work in my case. I'm building an iPad photo album app that will allow users to filter their results based on keywords and a couple of other attributes associated with each photo. The attributes would be basic stuff like orientation and whether its color or not. Keywords will be based on a set of defined values that the user will have to choose from.

Here's a rough outline of what I have in the Core Data Model so far:
Entities (attributes):
Photos (id, title, desc, file path)
Keywords (id, name)

Since a photo can have multiple keywords associated with it, do I create a relationship from 'Photos' with a destination of 'Keywords' and make it a -to many relationship? Is that correct/crazy/completely wrong? How would I go about adding/fetching records for that relationship?

Upvotes: 0

Views: 289

Answers (2)

Daniel
Daniel

Reputation: 23359

If the Keywords are defined and the user can choose them from a defined list, I wouldn't have used an entity Keyword. Tip always use singular names (Photo, Keyword). I would have the keywords in a plist and the user chooses a few, you could then create a comma separated string to save as a property on Photo. As Joseph mentioned, you want to subclass NSManagedObject and I would then add a method that receives a string (keyword) and returns a BOOL indicating if that keyword was part of the comma separated keyword values on the Photo property

Upvotes: 3

Joseph DeCarlo
Joseph DeCarlo

Reputation: 3278

This is correct. There are several approaches to accessing this, but the most straight-forward way is to generate NSManagedObject subclasses (Editor->Create NSManagedObject Subclass...). When populating these the Photo entity, the Keyword relationship will be populated in the property called keywords.

Upvotes: 1

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