Module: ActiveNode::FinderMethods
- Included in:
- Graph
- Defined in:
- lib/active_node/graph/finder_methods.rb
Instance Method Summary collapse
-
#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. -
#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. -
#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.
Instance Method Details
#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_node/graph/finder_methods.rb', line 62 def find(*args) if block_given? to_a.find { |*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_node/graph/finder_methods.rb', line 78 def find_by(*args) where(*args).take 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_node/graph/finder_methods.rb', line 84 def find_by!(*args) where(*args).take! 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
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 LIMIT 3
Rails 3
Person.first # SELECT "people".* FROM "people" LIMIT 1
NOTE: Rails 3 may not order this query by the primary key and the order will depend on the database implementation. In order to ensure that behavior, use User.order(:id).first
instead.
Rails 4
Person.first # SELECT "people".* FROM "people" ORDER BY "people"."id" ASC LIMIT 1
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# File 'lib/active_node/graph/finder_methods.rb', line 126 def first(limit = nil) if limit find_nth_with_limit(offset_value, limit) else find_nth(:first, offset_value) 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_node/graph/finder_methods.rb', line 136 def first! first or raise RecordNotFound 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_node/graph/finder_methods.rb', line 155 def last(limit = nil) if limit if order_values.empty? order(id: :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_node/graph/finder_methods.rb', line 169 def last! last or raise RecordNotFound 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_node/graph/finder_methods.rb', line 227 def raise_record_not_found_exception!(ids, result_size, expected_size) #:nodoc: if Array(ids).size == 1 error = "Couldn't find #{@klass.name} with 'id'=#{ids}#{conditions}" else error = "Couldn't find all #{@klass.name.pluralize} with 'id': " error << "(#{ids.join(", ")})#{conditions} (found #{result_size} results, but was looking for #{expected_size})" end raise RecordNotFound, error 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_node/graph/finder_methods.rb', line 95 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_node/graph/finder_methods.rb', line 101 def take! take or raise RecordNotFound end |