Model foreign key validation

Question

I have two models: Client and Invoice. Every client can have many invoices, every invoice belongs to only one client. If the client is deleted, the invoices with reference to him should be deleted, too.

This is all done through the following code:

#### Invoice class
class Invoice < ActiveRecord::Base
  attr_accessible :amount, :body, :client_id, :filename, :subject

  validates :amount, :body, :client_id, :filename, :subject, :presence => true
  validates :client_id, :numericality => { :only_integer => true, :greater_than_or_equal_to => 0 }

  belongs_to :client
end

#### Client class
class Client < ActiveRecord::Base
  attr_accessible :city, :country, :name, :street, :zip

  validates :city, :country, :name, :street, :zip, :presence => true
  validates :zip, :numericality => { :only_integer => true, :greater_than_or_equal_to => 10000, :less_than_or_equal_to => 99999 }

  has_many :invoices, dependent: :destroy
end

This is what I have built so far - but I am wondering: How can I validate that when a user creates a new invoice, the client id in the client table actually exists, and if not, display an according error message?

score 5 · Accepted Answer · edited May 23 '17 at 12:16

5

For foreign key (FK) constraints, I would recommend you do that in your database. Rails itself has no built-in support for that. If you do want to check foreign keys' existence in Ruby/Rails, that would add unnecessary load to the application.

Here are several links might help:

You Should Use Foreign Key Constraints in Rails

Support for foreign key constraint in Rails

Adding foreign key constraints in rails migrations

edited May 23 '17 at 12:16

Community

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answered Sep 15 '12 at 01:48

inntran

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Thank you! This is all fine, I just need to tell the user that the id doesn't exist if that's the case. How would you do that? Is there any way to do that in the model? – Dennis Hackethal Sep 15 '12 at 02:22
FYI, your first link is now broken. – ashes999 Feb 06 '15 at 23:07

Dennis Hackethal · Answer 2 · 2015-01-29T22:12:04.993

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Slightly updated answer; in Rails 4.2, you can make use of the new required option on singular associations.

class Invoice < ActiveRecord::Base
  belongs_to :client, required: true
end

Rails 4.2 also supports this on has_one associations:

has_one :foo, required: true

Here is the PR: https://github.com/rails/rails/pull/16056

edited Jan 29 '15 at 22:12

answered Jan 29 '15 at 21:59

Dennis Hackethal

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Model foreign key validation

2 Answers2