From: Yaw Boakye via ruby-core <ruby-core@...>
Date: 2023-10-08T20:29:29+01:00
Subject: [ruby-core:114982] Re: [Ruby master Feature#19884] Make Safe Navigation Operator work on classes

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How may `defined!?` be different from `Object#const_get` which is able to
lookup and load a constant given its name?

On Sun 8 Oct 2023 at 11:41, p8 (Petrik de Heus) via ruby-core <
ruby-core@ml.ruby-lang.org> wrote:

> Issue #19884 has been updated by p8 (Petrik de Heus).
>
>
> nobu (Nobuyoshi Nakada) wrote in #note-10:
> > Rather the extension of `defined?` operator which returns the value
> (instead of the expression type string) or nil.
> >
> > Let's call it `defined=E2=81=89=EF=B8=8F` for now.
> > Isn't this what you want?
> >
> > ```ruby
> > defined=E2=81=89=EF=B8=8F(OptionalDependency)&.some_method
> > ```
>
> Yes, that would be nice.
>
> ----------------------------------------
> Feature #19884: Make Safe Navigation Operator work on classes
> https://bugs.ruby-lang.org/issues/19884#change-104853
>
> * Author: p8 (Petrik de Heus)
> * Status: Open
> * Priority: Normal
> ----------------------------------------
> If a constant isn't defined it will raise a NameError:
>
> ```ruby
> DoesNotExist.some_method # raises: uninitialized constant DoesNotExist
> (NameError)
> ```
>
> In libraries that have optional dependencies, we can check if the constan=
t
> is defined before calling a method on it:
>
> ```ruby
> defined?(OptionalDependency) && OptionalDependency.some_method
>
> ```
>
> Currently in Ruby, the Safe Navigation Operator is used to avoid
> NoMethodError exceptions when calling methods on objects that may be nil.
> It would be nice if we could use the Safe Navigation Operator to avoid
> NameError on undefined constants as well.
>
> ```ruby
> ClassThatMightNotExist&.some_method
>
> ```
>
>
>
> --
> https://bugs.ruby-lang.org/
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<div dir=3D"auto">How may `defined!?` be different from `Object#const_get` =
which is able to lookup and load a constant given its name?</div><div><br><=
div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sun 8 Oc=
t 2023 at 11:41, p8 (Petrik de Heus) via ruby-core &lt;<a href=3D"mailto:ru=
by-core@ml.ruby-lang.org">ruby-core@ml.ruby-lang.org</a>&gt; wrote:<br></di=
v><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;borde=
r-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color=
:rgb(204,204,204)">Issue #19884 has been updated by p8 (Petrik de Heus).<br=
>
<br>
<br>
nobu (Nobuyoshi Nakada) wrote in #note-10: <br>
&gt; Rather the extension of `defined?` operator which returns the value (i=
nstead of the expression type string) or nil.<br>
&gt; <br>
&gt; Let&#39;s call it `defined=E2=81=89=EF=B8=8F` for now.<br>
&gt; Isn&#39;t this what you want?<br>
&gt; <br>
&gt; ```ruby<br>
&gt; defined=E2=81=89=EF=B8=8F(OptionalDependency)&amp;.some_method<br>
&gt; ```<br>
<br>
Yes, that would be nice.<br>
<br>
----------------------------------------<br>
Feature #19884: Make Safe Navigation Operator work on classes<br>
<a href=3D"https://bugs.ruby-lang.org/issues/19884#change-104853" rel=3D"no=
referrer" target=3D"_blank">https://bugs.ruby-lang.org/issues/19884#change-=
104853</a><br>
<br>
* Author: p8 (Petrik de Heus)<br>
* Status: Open<br>
* Priority: Normal<br>
----------------------------------------<br>
If a constant isn&#39;t defined it will raise a NameError:<br>
<br>
```ruby<br>
DoesNotExist.some_method # raises: uninitialized constant DoesNotExist (Nam=
eError)<br>
```<br>
<br>
In libraries that have optional dependencies, we can check if the constant =
is defined before calling a method on it:<br>
<br>
```ruby<br>
defined?(OptionalDependency) &amp;&amp; OptionalDependency.some_method<br>
<br>
```<br>
<br>
Currently in Ruby, the Safe Navigation Operator is used to avoid NoMethodEr=
ror exceptions when calling methods on objects that may be nil.<br>
It would be nice if we could use the Safe Navigation Operator to avoid Name=
Error on undefined constants as well.<br>
<br>
```ruby<br>
ClassThatMightNotExist&amp;.some_method<br>
<br>
```<br>
<br>
<br>
<br>
-- <br>
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">https://bugs.ruby-lang.org/</a><br>
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