From: zverok.offline@gmail.com
To: ruby-core@ruby-lang.org
Subject: [ruby-core:102225] [Ruby master Feature#17330] Object#non
Date: Sun, 24 Jan 2021 09:31:07 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-90075.20210124093104.710@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-17330.20201117124902.710@ruby-lang.org
Issue #17330 has been updated by zverok (Victor Shepelev).
@nobu
> This seems readable enough and more flexible.
```ruby
return Faraday.get(url).then {_1.body if _1.successful?}
```
I argue that the idiom (return something/continue with something, conditionally) is so frequent, that it should be more atomic.
> Or, make `successful?` to return `self` or `nil`
That's what I started this ticket with!
* This is not natural for Ruby: `nonzero?` is frequently mocked and generally considered a "design error"; Rails' `presence` has kind of the same vibe
* This requires me to change Faraday (which, to be clear, I have no relation to), and then go and change every library which causes the same idiom :)
* This is solving very particular case (just like `nonzero?` and `presence`), I am talking about generic.
Here's one more example:
```ruby
Faraday.get(url).body.then { JSON.parse(_1, symbolize_names: true) }.non { _1.key?('error') }&.dig('user', 'status')
```
----------------------------------------
Feature #17330: Object#non
https://bugs.ruby-lang.org/issues/17330#change-90075
* 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}") }
```
### Possible extensions of the idea
It is quite tempting to define the symmetric method named -- as we already have `Object#then` -- `Object#when`:
```ruby
some.long.calculation.when { |val| val < 10 } # returns nil if value >= 10
# or even... with support for ===
some.long.calculation.when(..10)&.then { continue to do something }
```
...but I am afraid I've overstayed my welcome :)
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2021-01-24 9:31 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 12:49 [ruby-core:100897] [Ruby master Feature#17330] Object#non zverok.offline
2020-11-17 12:55 ` [ruby-core:100898] " nobu
2021-01-02 9:46 ` [ruby-core:101876] " sawadatsuyoshi
2021-01-12 5:40 ` [ruby-core:102017] " akr
2021-01-13 7:07 ` [ruby-core:102054] " matz
2021-01-23 16:41 ` [ruby-core:102222] " zverok.offline
2021-01-24 2:42 ` [ruby-core:102223] " nobu
2021-01-24 9:31 ` zverok.offline [this message]
2021-01-25 15:54 ` [ruby-core:102236] " daniel
2022-08-08 7:51 ` [ruby-core:109446] " byroot (Jean Boussier)
2022-08-10 17:48 ` [ruby-core:109467] " Dan0042 (Daniel DeLorme)
2022-08-16 15:02 ` [ruby-core:109497] " mame (Yusuke Endoh)
2022-08-16 15:23 ` [ruby-core:109501] " zverok (Victor Shepelev)
2022-08-16 16:19 ` [ruby-core:109504] " mame (Yusuke Endoh)
2022-08-16 17:53 ` [ruby-core:109506] " Dan0042 (Daniel DeLorme)
2022-08-17 3:23 ` [ruby-core:109507] " ujihisa (Tatsuhiro Ujihisa)
2022-08-17 4:46 ` [ruby-core:109508] " sawa (Tsuyoshi Sawada)
2022-08-17 5:13 ` [ruby-core:109509] " zverok (Victor Shepelev)
2022-08-17 5:36 ` [ruby-core:109510] " hmdne (hmdne -)
2022-08-17 14:30 ` [ruby-core:109514] " Dan0042 (Daniel DeLorme)
2022-08-19 5:09 ` [ruby-core:109565] " matz (Yukihiro Matsumoto)
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