Merge branch 'master' of github.com:rails/docrails

activerecord/lib/active_record/relation/finder_methods.rb

@@ -11,7 +11,9 @@ module FinderMethods
     #   Person.find([1])     # returns an array for the object with ID = 1
     #   Person.where("administrator = 1").order("created_on DESC").find(1)
     #
-    # Note that returned records may not be in the same order as the ids you
+    # NOTE: An RecordNotFound will be raised if one or more ids are not returned.
+    #
+    # NOTE: that returned records may not be in the same order as the ids you
     # provide since database rows are unordered. Give an explicit <tt>order</tt>
     # to ensure the results are sorted.
     #
@@ -28,6 +30,38 @@ module FinderMethods
     #     person.visits += 1
     #     person.save!
     #   end
+    #
+    # ==== Variations of +find+
+    # 
+    #   Person.where(name: 'Spartacus', rating: 4)
+    #   # returns a chainable list (which can be empty)
+    #
+    #   Person.find_by(name: 'Spartacus', rating: 4)
+    #   # returns the first item or nil
+    #
+    #   Person.where(name: 'Spartacus', rating: 4).first_or_initialize
+    #   # returns the first item or returns a new instance (requires you call .save to persist against the database)
+    #
+    #   Person.where(name: 'Spartacus', rating: 4).first_or_create
+    #   # returns the first item or creates it and returns it, available since rails 3.2.1
+    #
+    #   
+    # ==== Alternatives for +find+
+    #
+    #   Person.where(name: 'Spartacus', rating: 4).exists?(conditions = :none)
+    #   # returns true or false
+    #   
+    #   Person.where(name: 'Spartacus', rating: 4).select("field1, field2, field3")
+    #   # returns a chainable list of instances with only the mentioned fields
+    #
+    #   Person.where(name: 'Spartacus', rating: 4).ids
+    #   # returns an Array of ids, available since rails 3.2.1
+    #
+    #   Person.where(name: 'Spartacus', rating: 4).pluck(:field1, :field2)
+    #   # returns an Array of the required fields, available since rails 3.1
+    #
+    #   Person.arel_table
+    #   # returns an instance of <tt>Arel::Table</tt>, which allows a comprehensive variety of filters
     def find(*args)
       if block_given?
         to_a.find { |*block_args| yield(*block_args) }
@@ -79,6 +113,19 @@ def take!
     #   Person.where(["user_name = :u", { u: user_name }]).first
     #   Person.order("created_on DESC").offset(5).first
     #   Person.first(3) # returns the first three objects fetched by SELECT * FROM people LIMIT 3
+    #
+    # ==== Rails 3
+    #
+    #   Person.first # SELECT "people".* FROM "people" LIMIT 1
+    #
+    # NOTE: Rails 3 may not +order+ this query by be the primary key.
+    # The order will depend on the database implementation.
+    # In order to ensure that behavior use <tt>User.order(:id).first</tt> instead.
+    #
+    # ==== Rails 4
+    #
+    #   Person.first # SELECT "people".* FROM "people" ORDER BY "people"."id" ASC LIMIT 1
+    #
     def first(limit = nil)
       if limit
         if order_values.empty? && primary_key