Merge pull request #2757 from andmej/first_or_create_pull_request

Add first_or_create family of methods to Active Record

activerecord/CHANGELOG

@@ -4,6 +4,12 @@ Wed Sep  7 15:25:02 2011  Aaron Patterson <aaron@tenderlovemaking.com>
 	  keys are per process id.
 	* lib/active_record/connection_adapters/sqlite_adapter.rb: ditto
 
+* Add first_or_create, first_or_create!, first_or_build and first_or_new methods to Active Record. This is a better approach over the old find_or_create_by dynamic methods because it's clearer which arguments are used to find the record and which are used to create it:
+
+    User.where(:first_name => "Scarlett").first_or_create!(:last_name => "Johansson", :hot => true)
+
+  [Andrés Mejía]
+
 * Support bulk change_table in mysql2 adapter, as well as the mysql one. [Jon Leighton]
 
 * If multiple parameters are sent representing a date, and some are blank, the

activerecord/lib/active_record/base.rb

@@ -442,6 +442,7 @@ class Base
 
     class << self # Class methods
       delegate :find, :first, :first!, :last, :last!, :all, :exists?, :any?, :many?, :to => :scoped
+      delegate :first_or_create, :first_or_create!, :first_or_new, :first_or_build, :to => :scoped
       delegate :destroy, :destroy_all, :delete, :delete_all, :update, :update_all, :to => :scoped
       delegate :find_each, :find_in_batches, :to => :scoped
       delegate :select, :group, :order, :except, :reorder, :limit, :offset, :joins, :where, :preload, :eager_load, :includes, :from, :lock, :readonly, :having, :create_with, :to => :scoped

activerecord/lib/active_record/relation.rb

@@ -94,6 +94,49 @@ def create!(*args, &block)
       scoping { @klass.create!(*args, &block) }
     end
 
+    # Tries to load the first record; if it fails, then <tt>create</tt> is called with the same arguments as this method.
+    #
+    # Expects arguments in the same format as <tt>Base.create</tt>.
+    #
+    # ==== Examples
+    #   # Find the first user named Penélope or create a new one.
+    #   User.where(:first_name => 'Penélope').first_or_create
+    #   # => <User id: 1, first_name: 'Penélope', last_name: nil>
+    #
+    #   # Find the first user named Penélope or create a new one.
+    #   # We already have one so the existing record will be returned.
+    #   User.where(:first_name => 'Penélope').first_or_create
+    #   # => <User id: 1, first_name: 'Penélope', last_name: nil>
+    #
+    #   # Find the first user named Scarlett or create a new one with a particular last name.
+    #   User.where(:first_name => 'Scarlett').first_or_create(:last_name => 'Johansson')
+    #   # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+    #
+    #   # Find the first user named Scarlett or create a new one with a different last name.
+    #   # We already have one so the existing record will be returned.
+    #   User.where(:first_name => 'Scarlett').first_or_create do |user|
+    #     user.last_name = "O'Hara"
+    #   end
+    #   # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+    def first_or_create(attributes = nil, options = {}, &block)
+      first || create(attributes, options, &block)
+    end
+
+    # Like <tt>first_or_create</tt> but calls <tt>create!</tt> so an exception is raised if the created record is invalid.
+    #
+    # Expects arguments in the same format as <tt>Base.create!</tt>.
+    def first_or_create!(attributes = nil, options = {}, &block)
+      first || create!(attributes, options, &block)
+    end
+
+    # Like <tt>first_or_create</tt> but calls <tt>new</tt> instead of <tt>create</tt>.
+    #
+    # Expects arguments in the same format as <tt>Base.new</tt>.
+    def first_or_new(attributes = nil, options = {}, &block)
+      first || new(attributes, options, &block)
+    end
+    alias :first_or_build :first_or_new
+
     def respond_to?(method, include_private = false)
       arel.respond_to?(method, include_private)     ||
         Array.method_defined?(method)               ||

activerecord/test/cases/base_test.rb

@@ -278,6 +278,37 @@ def test_create_after_initialize_with_block
     assert_equal(true, cb.frickinawesome)
   end
 
+  def test_first_or_create
+    parrot = Bird.first_or_create(:color => 'green', :name => 'parrot')
+    assert parrot.persisted?
+    the_same_parrot = Bird.first_or_create(:color => 'yellow', :name => 'macaw')
+    assert_equal parrot, the_same_parrot
+  end
+
+  def test_first_or_create_bang
+    assert_raises(ActiveRecord::RecordInvalid) { Bird.first_or_create! }
+    parrot = Bird.first_or_create!(:color => 'green', :name => 'parrot')
+    assert parrot.persisted?
+    the_same_parrot = Bird.first_or_create!(:color => 'yellow', :name => 'macaw')
+    assert_equal parrot, the_same_parrot
+  end
+
+  def test_first_or_new
+    parrot = Bird.first_or_new(:color => 'green', :name => 'parrot')
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert parrot.new_record?
+    assert parrot.valid?
+  end
+
+  def test_first_or_build
+    parrot = Bird.first_or_build(:color => 'green', :name => 'parrot')
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert parrot.new_record?
+    assert parrot.valid?
+  end
+
   def test_load
     topics = Topic.find(:all, :order => 'id')
     assert_equal(4, topics.size)

activerecord/test/cases/relations_test.rb

@@ -863,6 +863,134 @@ def test_create_bang
     assert_equal 'hen', hen.name
   end
 
+  def test_first_or_create
+    parrot = Bird.where(:color => 'green').first_or_create(:name => 'parrot')
+    assert_kind_of Bird, parrot
+    assert parrot.persisted?
+    assert_equal 'parrot', parrot.name
+    assert_equal 'green', parrot.color
+
+    same_parrot = Bird.where(:color => 'green').first_or_create(:name => 'parakeet')
+    assert_kind_of Bird, same_parrot
+    assert same_parrot.persisted?
+    assert_equal parrot, same_parrot
+  end
+
+  def test_first_or_create_with_no_parameters
+    parrot = Bird.where(:color => 'green').first_or_create
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert_equal 'green', parrot.color
+  end
+
+  def test_first_or_create_with_block
+    parrot = Bird.where(:color => 'green').first_or_create { |bird| bird.name = 'parrot' }
+    assert_kind_of Bird, parrot
+    assert parrot.persisted?
+    assert_equal 'green', parrot.color
+    assert_equal 'parrot', parrot.name
+
+    same_parrot = Bird.where(:color => 'green').first_or_create { |bird| bird.name = 'parakeet' }
+    assert_equal parrot, same_parrot
+  end
+
+  def test_first_or_create_with_array
+    several_green_birds = Bird.where(:color => 'green').first_or_create([{:name => 'parrot'}, {:name => 'parakeet'}])
+    assert_kind_of Array, several_green_birds
+    several_green_birds.each { |bird| assert bird.persisted? }
+
+    same_parrot = Bird.where(:color => 'green').first_or_create([{:name => 'hummingbird'}, {:name => 'macaw'}])
+    assert_kind_of Bird, same_parrot
+    assert_equal several_green_birds.first, same_parrot
+  end
+
+  def test_first_or_create_bang_with_valid_options
+    parrot = Bird.where(:color => 'green').first_or_create!(:name => 'parrot')
+    assert_kind_of Bird, parrot
+    assert parrot.persisted?
+    assert_equal 'parrot', parrot.name
+    assert_equal 'green', parrot.color
+
+    same_parrot = Bird.where(:color => 'green').first_or_create!(:name => 'parakeet')
+    assert_kind_of Bird, same_parrot
+    assert same_parrot.persisted?
+    assert_equal parrot, same_parrot
+  end
+
+  def test_first_or_create_bang_with_invalid_options
+    assert_raises(ActiveRecord::RecordInvalid) { Bird.where(:color => 'green').first_or_create!(:pirate_id => 1) }
+  end
+
+  def test_first_or_create_bang_with_no_parameters
+    assert_raises(ActiveRecord::RecordInvalid) { Bird.where(:color => 'green').first_or_create! }
+  end
+
+  def test_first_or_create_bang_with_valid_block
+    parrot = Bird.where(:color => 'green').first_or_create! { |bird| bird.name = 'parrot' }
+    assert_kind_of Bird, parrot
+    assert parrot.persisted?
+    assert_equal 'green', parrot.color
+    assert_equal 'parrot', parrot.name
+
+    same_parrot = Bird.where(:color => 'green').first_or_create! { |bird| bird.name = 'parakeet' }
+    assert_equal parrot, same_parrot
+  end
+
+  def test_first_or_create_bang_with_invalid_block
+    assert_raise(ActiveRecord::RecordInvalid) do
+      parrot = Bird.where(:color => 'green').first_or_create! { |bird| bird.pirate_id = 1 }
+    end
+  end
+
+  def test_first_or_create_with_valid_array
+    several_green_birds = Bird.where(:color => 'green').first_or_create!([{:name => 'parrot'}, {:name => 'parakeet'}])
+    assert_kind_of Array, several_green_birds
+    several_green_birds.each { |bird| assert bird.persisted? }
+
+    same_parrot = Bird.where(:color => 'green').first_or_create!([{:name => 'hummingbird'}, {:name => 'macaw'}])
+    assert_kind_of Bird, same_parrot
+    assert_equal several_green_birds.first, same_parrot
+  end
+
+  def test_first_or_create_with_invalid_array
+    assert_raises(ActiveRecord::RecordInvalid) { Bird.where(:color => 'green').first_or_create!([ {:name => 'parrot'}, {:pirate_id => 1} ]) }
+  end
+
+  def test_first_or_new
+    parrot = Bird.where(:color => 'green').first_or_new(:name => 'parrot')
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert parrot.valid?
+    assert parrot.new_record?
+    assert_equal 'parrot', parrot.name
+    assert_equal 'green', parrot.color
+  end
+
+  def test_first_or_new_with_no_parameters
+    parrot = Bird.where(:color => 'green').first_or_new
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert !parrot.valid?
+    assert parrot.new_record?
+    assert_equal 'green', parrot.color
+  end
+
+  def test_first_or_new_with_block
+    parrot = Bird.where(:color => 'green').first_or_new { |bird| bird.name = 'parrot' }
+    assert_kind_of Bird, parrot
+    assert !parrot.persisted?
+    assert parrot.valid?
+    assert parrot.new_record?
+    assert_equal 'green', parrot.color
+    assert_equal 'parrot', parrot.name
+  end
+
+  def test_first_or_build_is_alias_for_first_or_new
+    birds = Bird.scoped
+    assert birds.respond_to?(:first_or_build)
+    assert_equal birds.method(:first_or_new), birds.method(:first_or_build)
+  end
+
   def test_explicit_create_scope
     hens = Bird.where(:name => 'hen')
     assert_equal 'hen', hens.new.name

railties/guides/source/active_record_querying.textile

@@ -1018,23 +1018,84 @@ If you want to find both by name and locked, you can chain these finders togethe
 
 WARNING: Up to and including Rails 3.1, when the number of arguments passed to a dynamic finder method is lesser than the number of fields, say <tt>Client.find_by_name_and_locked("Ryan")</tt>, the behavior is to pass +nil+ as the missing argument. This is *unintentional* and this behavior will be changed in Rails 3.2 to throw an +ArgumentError+.
 
-There's another set of dynamic finders that let you find or create/initialize objects if they aren't found. These work in a similar fashion to the other finders and can be used like +find_or_create_by_first_name(params[:first_name])+. Using this will first perform a find and then create if the find returns +nil+. The SQL looks like this for +Client.find_or_create_by_first_name("Ryan")+:
+h3. Find or build a new object
+
+It's common that you need to find a record or create it if it doesn't exist. You can do that with the +first_or_create+ and +first_or_create!+ methods.
+
+h4. +first_or_create+
+
+The +first_or_create+ method checks whether +first+ returns +nil+ or not. If it does return +nil+, then +create+ is called. This is very powerful when coupled with the +where+ method. Let's see an example.
+
+Suppose you want to find a client named 'Andy', and if there's none, create one and additionally set his +locked+ attribute to false. You can do so by running:
+
+<ruby>
+Client.where(:first_name => 'Andy').first_or_create(:locked => false)
+# => <Client id: 1, first_name: "Andy", orders_count: 0, locked: false, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27">
+</ruby>
+
+The SQL generated by this method looks like this:
 
 <sql>
-SELECT * FROM clients WHERE (clients.first_name = 'Ryan') LIMIT 1
+SELECT * FROM clients WHERE (clients.first_name = 'Andy') LIMIT 1
 BEGIN
-INSERT INTO clients (first_name, updated_at, created_at, orders_count, locked)
-  VALUES('Ryan', '2008-09-28 15:39:12', '2008-09-28 15:39:12', 0, '0')
+INSERT INTO clients (created_at, first_name, locked, orders_count, updated_at) VALUES ('2011-08-30 05:22:57', 'Andy', 0, NULL, '2011-08-30 05:22:57')
 COMMIT
 </sql>
 
-+find_or_create+'s sibling, +find_or_initialize+, will find an object and if it does not exist will act similarly to calling +new+ with the arguments you passed in. For example:
++first_or_create+ returns either the record that already existed or the new record. In our case, we didn't already have a client named Andy so the record was created an returned.
+
+The new record might not be saved to the database; that depends on whether validations passed or not (just like +create+).
+
+It's also worth noting that +first_or_create+ takes into account the arguments of the +where+ method. In the example above we didn't explicitly pass a +:first_name => 'Andy'+ argument to +first_or_create+. However, that was used when creating the new record because it was already passed before to the +where+ method.
+
+NOTE: On previous versions of Rails you could do a similar thing with the +find_or_create_by+ method. Following our example, you could also run something like +Client.find_or_create_by_first_name(:first_name => "Andy", :locked => false)+. This method still works, but it's encouraged to use +first_or_create+ because it's more explicit on what arguments are used to _find_ the record and what arguments are used to _create_ it, resulting in less confusion overall.
+
+h4. +first_or_create!+
+
+You can also use +first_or_create!+ to raise an exception if the new record is invalid. Validations are not covered on this guide, but let's assume for a moment that you temporarily add
+
+<ruby>
+    validates :orders_count, :presence => true
+</ruby>
+
+to your +Client+ model. If you try to create a new +Client+ without passing an +orders_count+, the record will be invalid and an exception will be raised:
+
+<ruby>
+Client.where(:first_name => 'Andy').first_or_create!(:locked => false)
+# => ActiveRecord::RecordInvalid: Validation failed: Orders count can't be blank
+</ruby>
+
+NOTE: Be sure to check the extensive *Active Record Validations and Callbacks Guide* for more information about validations.
+
+h4. +first_or_new+
+
+The +first_or_new+ method will work just like +first_or_create+ but it will not call +create+ but +new+. This means that a new model instance will be created in memory but won't be saved to the database. Continuing with the +first_or_create+ example, we now want the client named 'Nick':
+
+<ruby>
+nick = Client.where(:first_name => 'Nick').first_or_new(:locked => false)
+# => <Client id: nil, first_name: "Nick", orders_count: 0, locked: false, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27">
+
+nick.persisted?
+# => false
+
+nick.new_record?
+# => true
+</ruby>
+
+Because the object is not yet stored in the database, the SQL generated looks like this:
+
+<sql>
+SELECT * FROM clients WHERE (clients.first_name = 'Nick') LIMIT 1
+</sql>
+
+When you want to save it to the database, just call +save+:
 
 <ruby>
-client = Client.find_or_initialize_by_first_name('Ryan')
+nick.save
+# => true
 </ruby>
 
-will either assign an existing client object with the name "Ryan" to the client local variable, or initialize a new object similar to calling +Client.new(:first_name => 'Ryan')+. From here, you can modify other fields in client by calling the attribute setters on it: +client.locked = true+ and when you want to write it to the database just call +save+ on it.
+Just like you can use *+build+* instead of *+new+*, you can use *+first_or_build+* instead of *+first_or_new+*.
 
 h3. Finding by SQL