rails-activerecord

Add a reference column migration in Rails 4

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Rails 4.x When you already have users and uploads tables and wish to add a new relationship between them. All you need to do is: just generate a migration using the following command: rails g migration AddUserToUploads user:references Which will create a migration file as: class AddUserToUploads < ActiveRecord::Migration def change add_reference :uploads, :user, index: … Read more

How do you delete an ActiveRecord object?

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It’s destroy and destroy_all methods, like user.destroy User.find(15).destroy User.destroy(15) User.where(age: 20).destroy_all User.destroy_all(age: 20) Alternatively you can use delete and delete_all which won’t enforce :before_destroy and :after_destroy callbacks or any dependent association options. User.delete_all(condition: ‘value’) will allow you to delete records without a primary key Note: from @hammady’s comment, user.destroy won’t work if User model has … Read more

Rails where condition using NOT NIL

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Rails 4+ ActiveRecord 4.0 and above adds where.not so you can do this: Foo.includes(:bar).where.not(‘bars.id’ => nil) Foo.includes(:bar).where.not(bars: { id: nil }) When working with scopes between tables, I prefer to leverage merge so that I can use existing scopes more easily. Foo.includes(:bar).merge(Bar.where.not(id: nil)) Also, since includes does not always choose a join strategy, you should … Read more

Rails update_attributes without save?

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I believe what you are looking for is assign_attributes. It’s basically the same as update_attributes but it doesn’t save the record: class User < ActiveRecord::Base attr_accessible :name attr_accessible :name, :is_admin, :as => :admin end user = User.new user.assign_attributes({ :name => ‘Josh’, :is_admin => true }) # Raises an ActiveModel::MassAssignmentSecurity::Error user.assign_attributes({ :name => ‘Bob’}) user.name # … Read more

How do you write a migration to rename an ActiveRecord model and its table in Rails?

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Here’s an example: class RenameOldTableToNewTable < ActiveRecord::Migration def self.up rename_table :old_table_name, :new_table_name end def self.down rename_table :new_table_name, :old_table_name end end I had to go and rename the model declaration file manually. Edit: In Rails 3.1 & 4, ActiveRecord::Migration::CommandRecorder knows how to reverse rename_table migrations, so you can do this: class RenameOldTableToNewTable < ActiveRecord::Migration def change … Read more

Rails 4: List of available datatypes

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Here are all the Rails 4 (ActiveRecord migration) datatypes: :binary :boolean :date :datetime :decimal :float :integer :bigint :primary_key :references :string :text :time :timestamp Source: http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_column These are the same as with Rails 3. If you use PostgreSQL, you can also take advantage of these: :hstore :json :jsonb :array :cidr_address :ip_address :mac_address They are stored as … Read more

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