I’m trying to set up a directional self-referential HABTM to represent
an arbitrary semi-hierarchical structure; it works for any data
prepopulated into the db, but when I try to create a new relationship,
I just get NULLs in both key columns (or 0’s if I turn on the no-null
constraint).
Here are the migrations:
class CreateNodes < ActiveRecord::Migration
def self.up
create_table :nodes do |t|
t.column :name, :string
end
end
def self.down
drop_table :nodes
end
end
class CreateNodesNodes < ActiveRecord::Migration
def self.up
create_table :nodes_nodes, :id => false do |t|
t.column :parent_id, :integer
t.column :child_id, :integer
end
end
def self.down
drop_table :nodes_nodes
end
end
And here is the model:
class Node < ActiveRecord::Base
has_and_belongs_to_many :parents, :foreign_key => :child_id,
:association_foreign_key
=> :parent_id,
:class_name => ‘Node’;
has_and_belongs_to_many :children, :foreign_key => :parent_id,
:association_foreign_key
=> :child_id,
:class_name => ‘Node’;
end
I’ve also tried swapping the foreign and association_foreign keys
around.
Any idea why this isn’t working? I’m using Rails 1.2.5 on MySQL, and
aside from the above code and the database.yml I haven’t touched
anything that “rails app” created.
ruby script/console
Loading development environment.p = Node.new
=> #<Node:0xb7192348 @new_record=true, @attributes={“name”=>nil}>p.name = ‘parent’
=> “parent”c = Node.new
=> #<Node:0xb714a8f4 @new_record=true, @attributes={“name”=>nil}>c.name = ‘child’
=> “child”>> p.children << c
=> [#<Node:0xb714a8f4 @new_record=true,
@attributes={“name”=>“child”}>]p.children
=> [#<Node:0xb714a8f4 @new_record=true,
@attributes={“name”=>“child”}>]c.parents
=> []p.save
=> truec.save
=> truep.reload
=> #<Node:0xb7192348 @new_record_before_save=true, @children=nil,
@new_record=false, @attributes={“name”=>“parent”, “id”=>“1”},
@parents=nil, @errors=#<ActiveRecord::Errors:0xb71251a8 @errors={},
@base=#<Node:0xb7192348 …>>>p.children
=> []c.reload
=> #<Node:0xb714a8f4 @children=nil, @new_record_before_save=false,
@new_record=false, @attributes={“name”=>“child”, “id”=>“2”},
@parents=nil, @errors=#<ActiveRecord::Errors:0xb7124f64 @errors={},
@base=#<Node:0xb714a8f4 …>>>c.parents
=> []