From: "mame (Yusuke Endoh)" Date: 2022-08-16T16:19:39+00:00 Subject: [ruby-core:109504] [Ruby master Feature#17330] Object#non Issue #17330 has been updated by mame (Yusuke Endoh). I understand the logic, but the result of your generalization, `&.non(&:empty?)`, is hard to read anyway. @matz says it too in #note-7. The short idiom includes a branch (`&.`), negation (`non`), and implicit Symbol#to_proc hack. It is very brain-intensive, and reminiscent of Perl. I guess the generalization is an impossible idea. I like the specific `container#nonempty?` in #12075 (except its name). If we were to introduce something even slightly generalized to this problem, `x.empty?.not` that @akr proposed in #note-6 would be a reasonable compromise, IMO. > The existence of `nonzero?` highlights that Ruby core devs also tried to address the problem. The birth of `nonzero?` is a bit more particular, and it is considered no longer needed in modern times. I wrote its history in https://bugs.ruby-lang.org/issues/9123#change-43083 . It is not so related to this topic, but you may be interested. ---------------------------------------- Feature #17330: Object#non https://bugs.ruby-lang.org/issues/17330#change-98673 * Author: zverok (Victor Shepelev) * Status: Open * Priority: Normal ---------------------------------------- (As always "with core" method proposals, I don't expect quick success, but hope for a fruitful discussion) ### Reasons: Ruby always tried to be very chainability-friendly. Recently, with introduction of `.then` and `=>`, even more so. But one pattern that frequently emerges and doesn't have good idiomatic expression: calculate something, and if it is not a "good" value, return `nil` (or provide default value with `||`). There are currently two partial solutions: 1. `nonzero?` in Ruby core (frequently mocked for "inadequate" behavior, as it is looking like predicate method, but instead of `true`/`false` returns an original value or `nil`) 2. ActiveSupport `Object#presence`, which also returns an original value or `nil` if it is not "present" (e.g. `nil` or `empty?` in AS-speak) Both of them prove themselves quite useful in some domains, but they are targeting only those particular domains, look unlike each other, and can be confusing. ### Proposal: Method `Object#non` (or `Kernel#non`), which receives a block, calls it with receiver and returns `nil` (if block matched) or receiver otherwise. ##### Prototype implementation: ```ruby class Object def non self unless yield(self) end end ``` ##### Usage examples: 1. With number: ```ruby limit = calculate.some.limit limit.zero? ? DEFAULT_LIMIT : limit # or, with nonzero? calculate.some.limit.nonzero? || DEFAULT_LIMIT # with non: calculate.some.limit.non(&:zero?) || DEFAULT_LIMIT # ^ Note here, how, unlike `nonzero?`, we see predicate-y ?, but it is INSIDE the `non()` and less confusing ``` 2. With string: ```ruby name = params[:name] if params[:name] && !params[:name].empty? # or, with ActiveSupport: name = params[:name].presence # with non: name = params[:name]&.non(&:empty?) ``` 3. More complicated example ```ruby action = payload.dig('action', 'type') return if PROHIBITED_ACTIONS.include?(action) send("do_#{action}") # with non & then: payload.dig('action', 'type') .non { |action| PROHIBITED_ACTIONS.include?(action) } &.then { |action| send("do_#{action}") } ``` Basically, the proposal is a "chainable guard clause" that allows to "chain"ify and DRYify code like: ```ruby value = fetch_something return value unless value.with_problems? # which turns into fetch_something.non(&:with_problems?) # or value = fetch_something value = reasonable_default if value.with_problems? # turns into value = fetch_something.non(&:with_problems?) || reasonable_default ``` I believe that this idiom is frequent enough, in combinations like (assorted examples) "read config file but return `nil` if it is empty/wrong version", "fetch latest invoice, but ignore if it has an `unpayable` flag", "fetch a list of last user's searches, but if it is empty, provide default search hints" etc. I believe there _is_ un unreflected need for idiom like this, the need that is demonstrated by the existence of `nonzero?` and `presence`. -- https://bugs.ruby-lang.org/ Unsubscribe: