From: duerst Date: 2021-09-02T00:28:52+00:00 Subject: [ruby-core:105110] [Ruby master Feature#18135] Introduce Enumerable#detect_only Issue #18135 has been updated by duerst (Martin D�rst). meisel (Michael Eisel) wrote in #note-2: > Also, another alternative could be `Enumerable#take_only`, where it takes the only element from the enumerable or else fails. So instead of: > ``` > array.detect_only { |elem| some_method(elem) } > ``` > > We'd have: > > ``` > array.select { |elem| some_method(elem) }.take_only > ``` It's a good idea to separate things out, but this could be highly inefficient (checking and selecting lots of elements only to find out later that there's more than one). ---------------------------------------- Feature #18135: Introduce Enumerable#detect_only https://bugs.ruby-lang.org/issues/18135#change-93520 * Author: meisel (Michael Eisel) * Status: Open * Priority: Normal ---------------------------------------- It can be important to get the only element for which a block returns true, and to assert that this is the only element as such. For example, this can be a very helpful sanity check when one is working with data that's outside of their control and is not perfectly understood. They may have a guess as to how to get a specific element matching some criteria, but if they used Enumerable#detect might be hiding the fact that they have written an incorrect block and that there's in fact more than one element that matches it. It could also be a parameter on Typically, I'd do it like this: ``` matches = array.select { |elem| some_method(elem) } raise if matches.size != 0 match = matches.first ``` Here, it would be shortened to: ``` match = array.detect_only { |elem| some_method(elem) } ``` It could also be a parameter on Enumerable#detect instead of a separate method. -- https://bugs.ruby-lang.org/ Unsubscribe: