Data modeling in CoreData, (folders and documents with many children, etc)

Question

Hi, I have used CoreData a couple of times but data modeling was very simple. This time I am supposed to implement the following:

• User can create documents and folders (they don't have to be real folders/directories).
• Folders can contain documents or other folders
• Documents have:
  • 1 Title,
  • 1 Description and
  • 8 children
• Each child also has a Title and a Description and could have 8 children (optionally)
• This could be as many levels (recursive) as the user desires.

I am not sure how to express this in CoreData. Could someone give a hand here? Right now I think of:

"Child" entity with "Title" "Description" as attributes and "Children" as a relationship (one to many). "File" entity with "IsFolder" as a boolean attribute and "Documents" as a relationship (one to many, pointing to "Child")

I am not sure if this well implements above structure in CoreData. I am in the right path? Re-modeling data structure in CoreData could be painful (I've heard) so i would like to have a good structure from the beginning. I hope I can get some advice from you;)

Thanks in advance.

Answer 1

You probably want something like this (pseudocode):

Folder{
    parent<<--(required,nullify)-->Folder.folders
    folders<--(optional,cascade)-->>Folder.parent
    documents<--(optional,cascade)-->>Document.folder
}

Document{
    title:string
    descriptionText:string
    parent<<--(optional,nullify)-->Document.children
    children<--(optional,cascade)-->>Document.parent
    folder<<--(optional,nullify)-->Folder.document
}

(Word of warning: Don't ever use "description" as an attribute name. NSObject has a description method so every subclass of NSObject responds to the description message. It will cause all kinds of ugly problems if you have an attribute accessor of the same name.)