Rails 7 adds Enumerable#sole

Rails 7 introduces the Enumerable#sole method, which can be used to find and assert the presence of exactly one element in the enumerable.

The Enumerable#sole method is an add-on for ActiveRecord::FinderMethods#sole and #find_sole_by methods, which were recently added in Rails 6.1. Please check our blog (Link is not available) for more details on it.

=> list = ["Sole Element"]
=> list.sole
=> "Sole Element"

=> hash = { foo: "bar" }
=> hash.sole
=> [:foo, "bar"]

The Enumerable#sole method raises Enumerable::SoleItemExpectedError error if the enumerable is empty or contains multiple elements. When the sole element is nil, it will be returned as result.

=> list = [nil]
=> list.sole
=> nil

=> list = []
=> list.sole
=> `Enumerable::SoleItemExpectedError (no item found)`

=> list = ["Apple", "Orange"]
=> list.sole
=> `Enumerable::SoleItemExpectedError (multiple items found)`

Check out this pull request for more details.