Module: ActiveRecord::FinderMethods
Relationships & Source Files | |
Extension / Inclusion / Inheritance Descendants | |
Included In:
ActiveRecord::AssociationRelation,
Associations::CollectionProxy ,
ActiveRecord::DisableJoinsAssociationRelation,
Relation
| |
Defined in: | activerecord/lib/active_record/relation/finder_methods.rb |
Constant Summary
-
ONE_AS_ONE =
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 7"1 AS one"
Instance Method Summary
-
#exists?(conditions = :none) ⇒ Boolean
Returns true if a record exists in the table that matches the
id
or conditions given, or false otherwise. -
#fifth
Find the fifth record.
-
#fifth!
Same as #fifth but raises
RecordNotFound
if no record is found. -
#find(*args)
Find by id - This can either be a specific id (ID), a list of ids (ID, ID, ID), or an array of ids ([ID, ID, ID]).
-
#find_by(arg, *args)
Finds the first record matching the specified conditions.
-
#find_by!(arg, *args)
Like #find_by, except that if no record is found, raises an
RecordNotFound
error. -
#find_sole_by(arg, *args)
Finds the sole matching record.
-
#first(limit = nil)
Find the first record (or first N records if a parameter is supplied).
-
#first!
Same as #first but raises
RecordNotFound
if no record is found. -
#forty_two
Find the forty-second record.
-
#forty_two!
Same as #forty_two but raises
RecordNotFound
if no record is found. -
#fourth
Find the fourth record.
-
#fourth!
Same as #fourth but raises
RecordNotFound
if no record is found. -
#include?(record) ⇒ Boolean
(also: #member?)
Returns true if the relation contains the given record or false otherwise.
-
#last(limit = nil)
Find the last record (or last N records if a parameter is supplied).
-
#last!
Same as #last but raises
RecordNotFound
if no record is found. -
#member?(record)
Alias for #include?.
-
#second
Find the second record.
-
#second!
Same as #second but raises
RecordNotFound
if no record is found. -
#second_to_last
Find the second-to-last record.
-
#second_to_last!
Same as #second_to_last but raises
RecordNotFound
if no record is found. -
#sole
Finds the sole matching record.
-
#take(limit = nil)
Gives a record (or N records if a parameter is supplied) without any implied order.
-
#take!
Same as #take but raises
RecordNotFound
if no record is found. -
#third
Find the third record.
-
#third!
Same as #third but raises
RecordNotFound
if no record is found. -
#third_to_last
Find the third-to-last record.
-
#third_to_last!
Same as #third_to_last but raises
RecordNotFound
if no record is found.
Instance Method Details
#exists?(conditions = :none) ⇒ Boolean
Returns true if a record exists in the table that matches the id
or conditions given, or false otherwise. The argument can take six forms:
-
::Integer
- Finds the record with this primary key. -
::String
- Finds the record with a primary key corresponding to this string (such as'5'
). -
::Array
- Finds the record that matches thesewhere
-style conditions (such as['name LIKE ?', "%#{query}%"]
). -
::Hash
- Finds the record that matches thesewhere
-style conditions (such as{name: 'David'}
). -
false
- Returns alwaysfalse
. -
No args - Returns
false
if the relation is empty,true
otherwise.
For more information about specifying conditions as a hash or array, see the Conditions section in the introduction to Base
.
Note: You can’t pass in a condition as a string (like name = 'Jamie'
), since it would be sanitized and then queried against the primary key column, like id = 'name = \'Jamie\''
.
Person.exists?(5)
Person.exists?('5')
Person.exists?(['name LIKE ?', "%#{query}%"])
Person.exists?(id: [1, 4, 8])
Person.exists?(name: 'David')
Person.exists?(false)
Person.exists?
Person.where(name: 'Spartacus', rating: 4).exists?
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 349
def exists?(conditions = :none) return false if @none if Base === conditions raise ArgumentError, <<-MSG.squish You are passing an instance of ActiveRecord::Base to `exists?`. Please pass the id of the object by calling `.id`. MSG end return false if !conditions || limit_value == 0 if eager_loading? relation = apply_join_dependency(eager_loading: false) return relation.exists?(conditions) end relation = construct_relation_for_exists(conditions) return false if relation.where_clause.contradiction? skip_query_cache_if_necessary { connection.select_rows(relation.arel, "#{name} Exists?").size == 1 } end
#fifth
Find the fifth record. If no order is defined it will order by primary key.
Person.fifth # returns the fifth object fetched by SELECT * FROM people
Person.offset(3).fifth # returns the fifth object from OFFSET 3 (which is OFFSET 7)
Person.where(["user_name = :u", { u: user_name }]).fifth
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 263
def fifth find_nth 4 end
#fifth!
Same as #fifth but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 269
def fifth! fifth || raise_record_not_found_exception! end
#find(*args)
Find by id - This can either be a specific id (ID), a list of ids (ID, ID, ID), or an array of ids ([ID, ID, ID]). ID
refers to an “identifier”. For models with a single-column primary key, ID
will be a single value, and for models with a composite primary key, it will be an array of values. If one or more records cannot be found for the requested ids, then RecordNotFound
will be raised. If the primary key is an integer, find by id coerces its arguments by using to_i
.
Person.find(1) # returns the object for ID = 1
Person.find("1") # returns the object for ID = 1
Person.find("31-sarah") # returns the object for ID = 31
Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
Person.find([7, 17]) # returns an array for objects with IDs in (7, 17), or with composite primary key [7, 17]
Person.find([1]) # returns an array for the object with ID = 1
Person.where("administrator = 1").order("created_on DESC").find(1)
Find a record for a composite primary key model
TravelRoute.primary_key = [:origin, :destination]
TravelRoute.find(["Ottawa", "London"])
#=> #<TravelRoute origin: "Ottawa", destination: "London">
TravelRoute.find([["Paris", "Montreal"]])
#=> [#<TravelRoute origin: "Paris", destination: "Montreal">]
TravelRoute.find(["New York", "Las Vegas"], ["New York", "Portland"])
#=> [
#<TravelRoute origin: "New York", destination: "Las Vegas">,
#<TravelRoute origin: "New York", destination: "Portland">
]
TravelRoute.find([["Berlin", "London"], ["Barcelona", "Lisbon"]])
#=> [
#<TravelRoute origin: "Berlin", destination: "London">,
#<TravelRoute origin: "Barcelona", destination: "Lisbon">
]
NOTE: The returned records are in the same order as the ids you provide. If you want the results to be sorted by database, you can use QueryMethods#where method and provide an explicit QueryMethods#order option. But QueryMethods#where method doesn’t raise RecordNotFound
.
Find with lock
Example for find with a lock: Imagine two concurrent transactions: each will read person.visits == 2
, add 1 to it, and save, resulting in two saves of person.visits = 3
. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4
.
Person.transaction do
person = Person.lock(true).find(1)
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.find_or_initialize_by(name: 'Spartacus', rating: 4)
# returns the first item or returns a new instance (requires you call .save to persist against the database).
Person.find_or_create_by(name: 'Spartacus', rating: 4)
# returns the first item or creates it and returns it.
Alternatives for #find
Person.where(name: 'Spartacus', rating: 4).exists?(conditions = :none)
# returns a boolean indicating if any record with the given conditions exist.
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.
Person.where(name: 'Spartacus', rating: 4).pluck(:field1, :field2)
# returns an Array of the required fields.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 90
def find(*args) return super if block_given? find_with_ids(*args) end
#find_by(arg, *args)
Finds the first record matching the specified conditions. There is no implied ordering so if order matters, you should specify it yourself.
If no record is found, returns nil
.
Post.find_by name: 'Spartacus', rating: 4
Post.find_by "published_at < ?", 2.weeks.ago
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 103
def find_by(arg, *args) where(arg, *args).take end
#find_by!(arg, *args)
Like #find_by, except that if no record is found, raises an RecordNotFound
error.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 109
def find_by!(arg, *args) where(arg, *args).take! end
#find_sole_by(arg, *args)
Finds the sole matching record. Raises RecordNotFound
if no record is found. Raises SoleRecordExceeded
if more than one record is found.
Product.find_sole_by(["price = %?", price])
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 152
def find_sole_by(arg, *args) where(arg, *args).sole end
#first(limit = nil)
Find the first record (or first N records if a parameter is supplied). If no order is defined it will order by primary key.
Person.first # returns the first object fetched by SELECT * FROM people ORDER BY people.id LIMIT 1
Person.where(["user_name = ?", user_name]).first
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 ORDER BY people.id LIMIT 3
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 165
def first(limit = nil) if limit find_nth_with_limit(0, limit) else find_nth 0 end end
#first!
Same as #first but raises RecordNotFound
if no record is found. Note that #first!
accepts no arguments.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 175
def first! first || raise_record_not_found_exception! end
#forty_two
Find the forty-second record. Also known as accessing “the reddit”. If no order is defined it will order by primary key.
Person.forty_two # returns the forty-second object fetched by SELECT * FROM people
Person.offset(3).forty_two # returns the forty-second object from OFFSET 3 (which is OFFSET 44)
Person.where(["user_name = :u", { u: user_name }]).forty_two
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 279
def forty_two find_nth 41 end
#forty_two!
Same as #forty_two but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 285
def forty_two! forty_two || raise_record_not_found_exception! end
#fourth
Find the fourth record. If no order is defined it will order by primary key.
Person.fourth # returns the fourth object fetched by SELECT * FROM people
Person.offset(3).fourth # returns the fourth object from OFFSET 3 (which is OFFSET 6)
Person.where(["user_name = :u", { u: user_name }]).fourth
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 247
def fourth find_nth 3 end
#fourth!
Same as #fourth but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 253
def fourth! fourth || raise_record_not_found_exception! end
#include?(record) ⇒ Boolean
Also known as: #member?
Returns true if the relation contains the given record or false otherwise.
No query is performed if the relation is loaded; the given record is compared to the records in memory. If the relation is unloaded, an efficient existence query is performed, as in #exists?.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 377
def include?(record) # The existing implementation relies on receiving an Active Record instance as the input parameter named record. # Any non-Active Record object passed to this implementation is guaranteed to return `false`. return false unless record.is_a?(klass) if loaded? || offset_value || limit_value || having_clause.any? records.include?(record) else id = if record.class.composite_primary_key? record.class.primary_key.zip(record.id).to_h else record.id end exists?(id) end end
#last(limit = nil)
Find the last record (or last N records if a parameter is supplied). If no order is defined it will order by primary key.
Person.last # returns the last object fetched by SELECT * FROM people
Person.where(["user_name = ?", user_name]).last
Person.order("created_on DESC").offset(5).last
Person.last(3) # returns the last three objects fetched by SELECT * FROM people.
Take note that in that last case, the results are sorted in ascending order:
[#<Person id:2>, #<Person id:3>, #<Person id:4>]
and not:
[#<Person id:4>, #<Person id:3>, #<Person id:2>]
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 194
def last(limit = nil) return find_last(limit) if loaded? || has_limit_or_offset? result = ordered_relation.limit(limit) result = result.reverse_order! limit ? result.reverse : result.first end
#last!
Same as #last but raises RecordNotFound
if no record is found. Note that #last!
accepts no arguments.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 205
def last! last || raise_record_not_found_exception! end
#member?(record)
Alias for #include?.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 395
alias :member? :include?
#second
Find the second record. If no order is defined it will order by primary key.
Person.second # returns the second object fetched by SELECT * FROM people
Person.offset(3).second # returns the second object from OFFSET 3 (which is OFFSET 4)
Person.where(["user_name = :u", { u: user_name }]).second
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 215
def second find_nth 1 end
#second!
Same as #second but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 221
def second! second || raise_record_not_found_exception! end
#second_to_last
Find the second-to-last record. If no order is defined it will order by primary key.
Person.second_to_last # returns the second-to-last object fetched by SELECT * FROM people
Person.offset(3).second_to_last # returns the second-to-last object from OFFSET 3
Person.where(["user_name = :u", { u: user_name }]).second_to_last
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 311
def second_to_last find_nth_from_last 2 end
#second_to_last!
Same as #second_to_last but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 317
def second_to_last! second_to_last || raise_record_not_found_exception! end
#sole
Finds the sole matching record. Raises RecordNotFound
if no record is found. Raises SoleRecordExceeded
if more than one record is found.
Product.where(["price = %?", price]).sole
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 135
def sole found, undesired = first(2) if found.nil? raise_record_not_found_exception! elsif undesired.present? raise ActiveRecord::SoleRecordExceeded.new(self) else found end end
#take(limit = nil)
Gives a record (or N records if a parameter is supplied) without any implied order. The order will depend on the database implementation. If an order is supplied it will be respected.
Person.take # returns an object fetched by SELECT * FROM people LIMIT 1
Person.take(5) # returns 5 objects fetched by SELECT * FROM people LIMIT 5
Person.where(["name LIKE '%?'", name]).take
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 120
def take(limit = nil) limit ? find_take_with_limit(limit) : find_take end
#take!
Same as #take but raises RecordNotFound
if no record is found. Note that #take!
accepts no arguments.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 126
def take! take || raise_record_not_found_exception! end
#third
Find the third record. If no order is defined it will order by primary key.
Person.third # returns the third object fetched by SELECT * FROM people
Person.offset(3).third # returns the third object from OFFSET 3 (which is OFFSET 5)
Person.where(["user_name = :u", { u: user_name }]).third
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 231
def third find_nth 2 end
#third!
Same as #third but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 237
def third! third || raise_record_not_found_exception! end
#third_to_last
Find the third-to-last record. If no order is defined it will order by primary key.
Person.third_to_last # returns the third-to-last object fetched by SELECT * FROM people
Person.offset(3).third_to_last # returns the third-to-last object from OFFSET 3
Person.where(["user_name = :u", { u: user_name }]).third_to_last
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 295
def third_to_last find_nth_from_last 3 end
#third_to_last!
Same as #third_to_last but raises RecordNotFound
if no record is found.
# File 'activerecord/lib/active_record/relation/finder_methods.rb', line 301
def third_to_last! third_to_last || raise_record_not_found_exception! end