Tweak relationships & AR loading question

rubyonrails-talk
1

Hi,

Imagine you have a model Guy. Pick a guy from your table. Maybe he is married and have children (single guys can't have children, can they?). So your are tempted to write:

class Guy < ActiveRecord::Base   has_many :children end

But if he is single, he can't have children. So you wan't to write:

class Guy < ActiveRecord::Base   if self.single     has_many :children   else     has_one :child   end end

This could work: in fact has_* is just a macro for a bunch of specific define_method. I am wrong?

But it doesn't: the loading of the class fails claiming for NoMethodError: undefined method `single' I don't understand: does AR loads relationships before defining accessors? And if I force attr_accessor :single, assuming AR will override it, I've got the same error. Does he parses the whole class seeking for relationship first?

Thanks for your help,

2

After going deeper in the source code, @attributes = attributes_from_column_definition is called in the initialize method of ActiveRecord::Base.

Actually, during the loading of the class, there is first:

ActiveRecord::Base.class_eval do   include ActiveRecord::Validations   ../..   include ActiveRecord::Associations   ../.. end

@attributes is not initialized yet. I thought ActiveRecord::Validations could help me, to see how it handles passed attributes, but I didn't understand the validates_each method (line 291). What's the send method? :confused: