Module: ActiveRecord::FinderMethods
- Included in:
- Relation
- Defined in:
- lib/active_record/relation/finder_methods.rb
Constant Summary collapse
- ONE_AS_ONE =
'1 AS one'
Instance Method Summary collapse
-
#exists?(conditions = :none) ⇒ Boolean
Returns
true
if a record exists in the table that matches theid
or conditions given, orfalse
otherwise. -
#fifth ⇒ Object
Find the fifth record.
-
#fifth! ⇒ Object
Same as
fifth
but raisesActiveRecord::RecordNotFound
if no record is found. -
#find(*args) ⇒ Object
Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]).
-
#find_by(*args) ⇒ Object
Finds the first record matching the specified conditions.
-
#find_by!(*args) ⇒ Object
Like
find_by
, except that if no record is found, raises anActiveRecord::RecordNotFound
error. -
#first(limit = nil) ⇒ Object
Find the first record (or first N records if a parameter is supplied).
-
#first! ⇒ Object
Same as
first
but raisesActiveRecord::RecordNotFound
if no record is found. -
#forty_two ⇒ Object
Find the forty-second record.
-
#forty_two! ⇒ Object
Same as
forty_two
but raisesActiveRecord::RecordNotFound
if no record is found. -
#fourth ⇒ Object
Find the fourth record.
-
#fourth! ⇒ Object
Same as
fourth
but raisesActiveRecord::RecordNotFound
if no record is found. -
#last(limit = nil) ⇒ Object
Find the last record (or last N records if a parameter is supplied).
-
#last! ⇒ Object
Same as
last
but raisesActiveRecord::RecordNotFound
if no record is found. -
#raise_record_not_found_exception!(ids, result_size, expected_size) ⇒ Object
This method is called whenever no records are found with either a single id or multiple ids and raises a
ActiveRecord::RecordNotFound
exception. -
#second ⇒ Object
Find the second record.
-
#second! ⇒ Object
Same as
second
but raisesActiveRecord::RecordNotFound
if no record is found. -
#take(limit = nil) ⇒ Object
Gives a record (or N records if a parameter is supplied) without any implied order.
-
#take! ⇒ Object
Same as
take
but raisesActiveRecord::RecordNotFound
if no record is found. -
#third ⇒ Object
Find the third record.
-
#third! ⇒ Object
Same as
third
but raisesActiveRecord::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 these
find
-style conditions (such as['name LIKE ?', "%#{query}%"]
). -
Hash - Finds the record that matches these
find
-style conditions (such as{name: 'David'}
). -
false
- Returns alwaysfalse
. -
No args - Returns
false
if the table is empty,true
otherwise.
For more information about specifying conditions as a hash or array, see the Conditions section in the introduction to ActiveRecord::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?
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# File 'lib/active_record/relation/finder_methods.rb', line 277 def exists?(conditions = :none) if Base === conditions conditions = conditions.id ActiveSupport::Deprecation.warn(<<-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 relation = apply_join_dependency(self, construct_join_dependency) return false if ActiveRecord::NullRelation === relation relation = relation.except(:select, :order).select(ONE_AS_ONE).limit(1) case conditions when Array, Hash relation = relation.where(conditions) else unless conditions == :none relation = relation.where(primary_key => conditions) end end connection.select_value(relation, "#{name} Exists", relation.arel.bind_values + relation.bind_values) ? true : false end |
#fifth ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 224 def fifth find_nth(4, offset_index) end |
#fifth! ⇒ Object
Same as fifth
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File 'lib/active_record/relation/finder_methods.rb', line 230 def fifth! find_nth! 4 end |
#find(*args) ⇒ Object
Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised. If the primary key is an integer, find by id coerces its arguments 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)
Person.find([1]) # returns an array for the object with ID = 1
Person.where("administrator = 1").order("created_on DESC").find(1)
ActiveRecord::RecordNotFound
will be raised if one or more ids are not found.
NOTE: The returned records may not be in the same order as the ids you provide since database rows are unordered. You’d need to provide an explicit order
option if you want the results are sorted.
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.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 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, 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.
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# File 'lib/active_record/relation/finder_methods.rb', line 67 def find(*args) if block_given? to_a.find(*args) { |*block_args| yield(*block_args) } else find_with_ids(*args) end end |
#find_by(*args) ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 83 def find_by(*args) where(*args).take rescue RangeError nil end |
#find_by!(*args) ⇒ Object
Like find_by
, except that if no record is found, raises an ActiveRecord::RecordNotFound
error.
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# File 'lib/active_record/relation/finder_methods.rb', line 91 def find_by!(*args) where(*args).take! rescue RangeError raise RecordNotFound, "Couldn't find #{@klass.name} with an out of range value" end |
#first(limit = nil) ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 123 def first(limit = nil) if limit find_nth_with_limit(offset_index, limit) else find_nth(0, offset_index) end end |
#first! ⇒ Object
Same as first
but raises ActiveRecord::RecordNotFound
if no record is found. Note that first!
accepts no arguments.
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# File 'lib/active_record/relation/finder_methods.rb', line 133 def first! find_nth! 0 end |
#forty_two ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 240 def forty_two find_nth(41, offset_index) end |
#forty_two! ⇒ Object
Same as forty_two
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File 'lib/active_record/relation/finder_methods.rb', line 246 def forty_two! find_nth! 41 end |
#fourth ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 208 def fourth find_nth(3, offset_index) end |
#fourth! ⇒ Object
Same as fourth
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File 'lib/active_record/relation/finder_methods.rb', line 214 def fourth! find_nth! 3 end |
#last(limit = nil) ⇒ Object
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>]
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# File 'lib/active_record/relation/finder_methods.rb', line 152 def last(limit = nil) if limit if order_values.empty? && primary_key order(arel_table[primary_key].desc).limit(limit).reverse else to_a.last(limit) end else find_last end end |
#last! ⇒ Object
Same as last
but raises ActiveRecord::RecordNotFound
if no record is found. Note that last!
accepts no arguments.
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# File 'lib/active_record/relation/finder_methods.rb', line 166 def last! last or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql}]") end |
#raise_record_not_found_exception!(ids, result_size, expected_size) ⇒ Object
This method is called whenever no records are found with either a single id or multiple ids and raises a ActiveRecord::RecordNotFound
exception.
The error message is different depending on whether a single id or multiple ids are provided. If multiple ids are provided, then the number of results obtained should be provided in the result_size
argument and the expected number of results should be provided in the expected_size
argument.
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# File 'lib/active_record/relation/finder_methods.rb', line 313 def raise_record_not_found_exception!(ids, result_size, expected_size) #:nodoc: conditions = arel.where_sql conditions = " [#{conditions}]" if conditions if Array(ids).size == 1 error = "Couldn't find #{@klass.name} with '#{primary_key}'=#{ids}#{conditions}" else error = "Couldn't find all #{@klass.name.pluralize} with '#{primary_key}': " error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})" end raise RecordNotFound, error end |
#second ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 176 def second find_nth(1, offset_index) end |
#second! ⇒ Object
Same as second
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File 'lib/active_record/relation/finder_methods.rb', line 182 def second! find_nth! 1 end |
#take(limit = nil) ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 104 def take(limit = nil) limit ? limit(limit).to_a : find_take end |
#take! ⇒ Object
Same as take
but raises ActiveRecord::RecordNotFound
if no record is found. Note that take!
accepts no arguments.
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# File 'lib/active_record/relation/finder_methods.rb', line 110 def take! take or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql}]") end |
#third ⇒ Object
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
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# File 'lib/active_record/relation/finder_methods.rb', line 192 def third find_nth(2, offset_index) end |
#third! ⇒ Object
Same as third
but raises ActiveRecord::RecordNotFound
if no record is found.
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# File 'lib/active_record/relation/finder_methods.rb', line 198 def third! find_nth! 2 end |