aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
-rw-r--r--activerecord/lib/active_record/relation/finder_methods.rb49
1 files changed, 48 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index ba222aac93..f373714007 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -11,7 +11,9 @@ module ActiveRecord
# 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 ActiveRecord
# 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 @@ module ActiveRecord
# 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