CODEWITHSUNDEEP
ruby-on-railsactiverecordbelongs-to
user7111748
user7111748

Reputation:

Rails ActiveRecord. how can I deal with belong_to more than one?

How can I define a Person model so that any Person can be assigned as the parent of another Person (as demonstrated in the Rails console below)? What columns would you need to define in the migration creating the table for Person?

irb(main):001:0> john = Person.create(name: "John")
irb(main):002:0> jim = Person.create(name: "Jim", parent: john)
irb(main):003:0> bob = Person.create(name: "Bob", parent: john)
irb(main):004:0> john.children.map(&:name)
=> ["Jim", "Bob"]

I unserstand than the answer is something around 

class People < ActiveRecord::Base
        has_many :children, class_name: "People", foreign_key: "parent_id"
        belongs_to :parent, class_name: "People" #Question HERE? how to deal with belong_to more than one?
end

class AddXXTOXXX <ActiveRecord::Migration
            def change
                create_table :peoples do |t|
                    t.add_column :name, string
                    t.add_column :parent, string
                    t.references :parent, index: true
                    t.timestamps
                end
            end
end

But what confused me is that everyone has two parents(mom and daddy), so does belongs_to still work in this case of scenario ?

Upvotes: 0

Views: 151

Answers (1)

SteveTurczyn
SteveTurczyn

Reputation: 36860

No, if you have multiple parents who can have multiple children, belongs_to is not appropriate.

You want has_many through:... which will use a join table... you can call it whatever you want but relationships seems appropriate.

Also, change your People class into Person class to follow rails conventions.

class Person < ActiveRecord::Base

  has_many :ancestors, class_name: 'Relationship', foreign_key: :child_id
  has_many :descendants, class_name: 'Relationship', foreign_key: :parent_id
  has_many :parents, through: :ancestors, class_name: 'Person', foreign_key: :parent_id
  has_many :children, through: :descendants, class_name: 'Person', foreign_key: :child_id

end

You can store additional information in the 'Relationship' table, if you want, such as "mother" or "father" and "son" or "daughter"... although that may be better inferred from Person sex if that exists.

Upvotes: 1

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