newbie q on activerecord - has_one and has_many on same table?

rubyonrails-talk
1

Hi I have a table where I need to identify one of the children as the "prime" child.

So, its like:

Parent   has_many :Child   has_one: Child :as :prime_child (?)

or something like that? Do I put something like prime_child_id in the Parent table? Thanks.

2

Parent   has_many :children   scope :primary, where(:role => 'primary')

Or something like that. The syntax of scope, or named_scope differs depending on the version of Rails, but you get the idea... You'll probably want to add code to make sure that only one child has the primary role for a particular parent.

HTH

3

JoshK wrote:

Hi I have a table where I need to identify one of the children as the "prime" child.

So, its like:

Parent   has_many :Child   has_one: Child :as :prime_child (?)

or something like that? Do I put something like prime_child_id in the Parent table? Thanks.

Yes. You should be able to do class Parent < AR::B   has_many :children # not :Child !   has_one :prime_child, :class_name => 'Child' end

The two associations are completely independent. The fact that they refer to the same child class and table is irrelevant.

Best,