I want to build something so that a person can have many email addresses and an email address has only one person, but because I also have another model called Company that also can have many email addresses, and I don't want to have columns company_id and person_id in the Emails table, so I thought I can do ...
has_many :person_emails has_many :emails, :through => :person_emails
belongs_to :person belongs_to :email
has_one :person_email has_one :person, :through => :person_email
What's happening now is that...
p = Person.first #=> "Nik" p.emails #=> shows all emails Nik has p.person_emails #=> shows all person_email joint table records for Nik
e = Email.first #=> one of Nik's email addresses e.person_email #=> shows this email's one and only one person_email joint table record e.person # fails saying that unknown column "people.email_id" in where-clause
I'd like... e.person #=> "Nik"
Does anyone have an idea what the problem might be?
Thank You
Your situation suggests using polymorphic associations, which are much cleaner than has_many :through
associations. For example:
class Person
has_many :emails, :as => :emailable
end
class Company
has_many :emails, :as => :emailable
end
class Email
belongs_to :emailable, :polymorphic => true
end
You can get rid of your PersonEmails
class entirely. In the database, your emails
table will look something like this:
create_table :emails do |t|
t.string :address
t.string :emailable_type
t.integer :emailable_id
end
The emailable_type
column stores the name of the associated model, in your case "Person"
or "Company"
, and the emailable_id
stores the id of the associated object. For more information see the Rails API documentation under "Polymorphic Associations".
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