CODEWITHSUNDEEP
ruby-on-railsvalidationruby-on-rails-4
Steve
Steve

Reputation: 826

Rails model foreign key validation

I need to validate the existence of a row referenced by a foreign key in one of my models. The situation is like this:

Project.rb

class Project < ActiveRecord::Base
  has_one :project_category

  # -----------------------------------------------------------------
  # this does not work because the attribute is actually called 
  # 'category_id' instead of the rails expected 'project_category_id'
  # -----------------------------------------------------------------
  validates :project_category, presence: true
end

Project Migration

class CreateProjects < ActiveRecord::Migration
  def change
    create_table :projects do |t|

      # ----------------------------------------------
      # this is why the column is called 'category_id'
      # ---------------------------------------------- 
      t.references :category, references: :project_categories, null: false

      # all of my other fields here, unimportant
    end
    add_foreign_key :projects, :project_categories, column: :category_id
  end
end

I know that I can write a custom validation method to check if the :category_id exists in the project_categories table but I would prefer to let rails handle the validation if there is a way, so I can keep my code DRY.

EDIT

ProjectCategory.rb

class ProjectCategory < ActiveRecord::Base
  belongs_to :project

  validates :name, presence: true, uniqueness: { case_sensitive: false }
end

ProjectCategory Migration

class CreateProjectCategories < ActiveRecord::Migration
  def change
    create_table :project_categories do |t|
      t.string :name, null: false
    end
  end
end

Upvotes: 0

Views: 440

Answers (1)

vee
vee

Reputation: 38645

It appears you only need to add the foreign_key option to your has_one declaration in order to specify the custom column name you've specified i.e. category_id instead of project_category_id. See Options for has_one for details.

# app/modeles/project.rb

class Project < ActiveRecord::Base
  has_one :project_category, foreign_key: 'category_id'

  # -----------------------------------------------------------------
  # this does not work because the attribute is actually called 
  # 'category_id' instead of the rails expected 'project_category_id'
  # -----------------------------------------------------------------
  validates :project_category, presence: true
end

Upvotes: 1

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