diff options
| -rw-r--r-- | activerecord/lib/active_record/relation/finder_methods.rb | 49 |
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 |