MongoDB mongoid self reference relationship

I开发者_运维问答 am new to mongo/mongoid and I am trying to setup a self referencing relationships on my sites table.

# sites model

has_many :child_sites, :class_name => 'Site'
belongs_to :parent, :class_name => 'Site'

#controller

@event = current_site.child_sites.build(params[:site])

current_site is a function that returns the current site object.

I get this error -

undefined method `entries' for #

You can try changing your relation definitions to the following:

has_many :child_sites, :class_name => 'Site', :cyclic => true
belongs_to :parent_site, :class_name => 'Site', :cyclic => true

I don't know exactly what it does, but I remember it being discussed in the Mongoid google group. If that doesn't work, you should try to set inverse_of on both the relation macros. Most of the time setting inverse_of correctly does the job.

has_many :child_sites, :class_name => 'Site', :inverse_of => :parent_site
belongs_to :parent_site, :class_name => 'Site', :inverse_of => :child_sites

About the extra queries, yes there would be extra queries whenever you want to fetch child_sites of a site or the parent site of a site.

You should consider embedding child sites in parent site, but keep in mind that way you would loose the ability to query child sites in a stand_alone manner. You would always have to access any child site as "parent_site > child_sites".

Also keep in mind the 16MB limit on size of document, which is hard to reach, but might be possible if there are a lot of child sites for a parent and if you are storing template info, like html, css etc. in the document itself.

Cyclic was originally implemented for embedded documents (see user group entry). To make this working on mongoid 2.3 or higher you have to remove the cyclic option:

has_many :child_sites, :class_name => 'Site'
belongs_to :parent_site, :class_name => 'Site'

Can't you use recursively_embeds_many or recursively_embeds_one? http://mongoid.org/en/mongoid/docs/relations.html#common