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revises the documentation of ActiveRecord::Relation#find_or_create_by…

… [ci skip]

* Inspect uses double quotes.

* Inspect puts a hash as in #<User ...>.

* Documents the return value, and makes explicit it can be an invalid record.

* Documents the method is not atomic.

* Documents a way to handle UNIQUE contraint violations in the event of a race condition.

* Removes the "Examples" header according to our guidelines.
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commit 81b3635783e78af316f5ac7cc1cb0a45c41f545b 1 parent d26e3a0
@fxn fxn authored
Showing with 38 additions and 14 deletions.
  1. +38 −14 activerecord/lib/active_record/relation.rb
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52 activerecord/lib/active_record/relation.rb
@@ -141,34 +141,58 @@ def first_or_initialize(attributes = nil, &block) # :nodoc:
first || new(attributes, &block)
end
- # Finds the first record with the given attributes, or creates a record with the attributes
- # if one is not found.
+ # Finds the first record with the given attributes, or creates a record
+ # with the attributes if one is not found:
#
- # ==== Examples
- # # Find the first user named Penélope or create a new one.
+ # # Find the first user named "Penélope" or create a new one.
# User.find_or_create_by(first_name: 'Penélope')
- # # => <User id: 1, first_name: 'Penélope', last_name: nil>
+ # # => #<User id: 1, first_name: "Penélope", last_name: nil>
#
- # # Find the first user named Penélope or create a new one.
+ # # Find the first user named "Penélope" or create a new one.
# # We already have one so the existing record will be returned.
# User.find_or_create_by(first_name: 'Penélope')
- # # => <User id: 1, first_name: 'Penélope', last_name: nil>
+ # # => #<User id: 1, first_name: "Penélope", last_name: nil>
#
- # # Find the first user named Scarlett or create a new one with a particular last name.
+ # # Find the first user named "Scarlett" or create a new one with
+ # # a particular last name.
# User.create_with(last_name: 'Johansson').find_or_create_by(first_name: 'Scarlett')
- # # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+ # # => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">
#
- # # Find the first user named Scarlett or create a new one with a different last name.
- # # We already have one so the existing record will be returned.
+ # This method accepts a block, which is passed down to +create+. The last example
+ # above can be alternatively written this way:
+ #
+ # # Find the first user named "Scarlett" or create a new one with a
+ # # different last name.
# User.find_or_create_by(first_name: 'Scarlett') do |user|
- # user.last_name = "O'Hara"
+ # user.last_name = 'Johansson'
# end
- # # => <User id: 2, first_name: 'Scarlett', last_name: 'Johansson'>
+ # # => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">
+ #
+ # This method always returns a record, but if creation was attempted and
+ # failed due to validation errors it won't be persisted, you get what
+ # +create+ returns in such situation.
+ #
+ # Please note *this method is not atomic*, it runs first a SELECT, and if
+ # there are no results an INSERT is attempted. If there are other threads
+ # or processes there is a race condition between both calls and it could
+ # be the case that you end up with two similar records.
+ #
+ # Whether that is a problem or not depends on the logic of the
+ # application, but in the particular case in which rows have a UNIQUE
+ # constraint an exception may be raised, just retry:
+ #
+ # begin
+ # CreditAccount.find_or_create_by(user_id: user.id)
+ # rescue ActiveRecord::RecordNotUnique
+ # retry
+ # end
+ #
def find_or_create_by(attributes, &block)
find_by(attributes) || create(attributes, &block)
end
- # Like <tt>find_or_create_by</tt>, but calls <tt>create!</tt> so an exception is raised if the created record is invalid.
+ # Like <tt>find_or_create_by</tt>, but calls <tt>create!</tt> so an exception
+ # is raised if the created record is invalid.
def find_or_create_by!(attributes, &block)
find_by(attributes) || create!(attributes, &block)
end
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