Jump to:

3373 Posts in 998 Topics by 712 members

Data Model Questions

SilverStripe Forums » Data Model Questions » Creating has_many relation with self

Moderators: martimiz, Sean, biapar, Willr, Ingo, swaiba, simon_w

Page: 1
Go to End
Author Topic: 2105 Views
  • zenmonkey
    Avatar
    Community Member
    524 Posts

    Creating has_many relation with self Link to this post

    Can a dataobject have a has_many relation with self. I'm trying to set up a list of definitions, then include related terms. So each term would have to have a has_many relation with other terms.

  • Willr
    Avatar
    Forum Moderator
    5462 Posts

    Re: Creating has_many relation with self Link to this post

    I think you would need a many_many relationship for that as a Definition would have many Related Terms and each of those Related terms would probably have multiple definition it relates to.

    You can try add a many_many / belongs_many_many to the object and try it out. I think it *should* be fine with a many_many relationship on itself. Try it out and see what happens

  • MichaelCole
    Avatar
    Community Member
    2 Posts

    Re: Creating has_many relation with self Link to this post

    From IRC:

    michaelcole: Hello!
    michaelcole: I'm just checking out Silverstripe. How could I model a "has many reference to self" relationship with the ORM?
    simon_w: static $has_many = array ('LotsOfMe'=>__CLASS__); static $has_one = array('OneOfMe' => __CLASS__);
    michaelcole: Cool! Sounds simple. I like it!

  • sekjal
    Avatar
    Community Member
    5 Posts

    Re: Creating has_many relation with self Link to this post

    Reviving this thread in the context of SilverStripe 3.0...

    I'm looking to create a Thesaurus module to support controlled vocabularies and relationships between terms:

    • Alternate Terms (Used For): many terms that are not current, or synonyms to the current term. Using a text field in $db for this now, with a modified search filter to include partial matches from this when searching for Terms.
    • Broader Terms (BT): possibly many more general Terms
    • Narrower Terms (NT): possibly many more specific Terms
    • Related Terms (RT): possibly many Terms with a different (non-hierarchical) relationship

    Broader Terms and Narrower Terms are inverses of each other, so I could define one of them in $many_many, and the other in $belongs_many_many. That way, when a Term has a Narrower Term, that Narrower Term lists the original term as a Broader Term. In abstract notation:

    if TermA is BT of TermB, then TermB is NT of TermA

    Related Terms, though, are bi-directional in themselves. In the same notation as above:

    if TermA is RT of TermB, then TermB is RT of TermA

    Is this kind of self-relationship possible without having to manually specify the inverse relationships? If the Data Model doesn't support it naturally, could a code block be added to insert the inverse relationship when the Related Term relationship is added? If so, where would that go and what would it need to look like?

    2105 Views
Page: 1
Go to Top

Want to know more about the company that brought you SilverStripe? Then check out SilverStripe.com

Comments on this website? Please give feedback.