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Date: Tue, 28 Oct 2014 09:46:30 +0000
Message-ID: <CAGAGxba5xcg7=fdM+QEd6-Q0fYurLNCANpnihhyiFbR_tNXTBg@mail.gmail.com>
To: Andrea Faulds <ajf@ajf.me>
Cc: Rowan Collins <rowan.collins@gmail.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Readonly Properties
From: cw@daverandom.com (Chris Wright)

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On 27 October 2014 20:27, Andrea Faulds <ajf@ajf.me> wrote:

>
> > On 26 Oct 2014, at 19:16, Rowan Collins <rowan.collins@gmail.com> wrote=
:
> >
> > I just had a thought on both the naming and future-proofing concerns of
> this proposal: what about pre-emptively reserving the skeleton of the
> syntax needed for accessors, without actually implementing them?
>
> I=E2=80=99ve been thinking about this. While `public readonly $foo;` does=
 work, it
> is confusing (only readonly to public) and limiting (no public/private
> option). Plus, while it could work with getters/setters, it=E2=80=99s har=
dly ideal.
>
> On the other hand, while having C#-style syntax here gives us a full
> feature set, I don=E2=80=99t like that it inverts the order of a declarat=
ion. To
> show you what I mean, here=E2=80=99s a normal property:
>
>     public $foobar;
>
> Now, here=E2=80=99s a property with C#-style syntax:
>
>     var $foobar { public get; private set; };
>
> See how the `public` moved to the right? I don=E2=80=99t like that, I wan=
t to
> avoid that if possible. I=E2=80=99m all for C#-style syntax with the get =
and set,
> but I don=E2=80=99t like that it moves the visibility specifier.
>
> Similarly, I don=E2=80=99t like this either:
>
>     public $foobar { get; private set; }
>
> Now the visibility is on both sides! Yuck. That=E2=80=99s the worst of bo=
th worlds.
>
> What I=E2=80=99d like is probably something like this:
>
>     public/private $foobar;
>
> Tentative syntax. But this way, the visibility stays on the left. I think
> that=E2=80=99s good for readability. If you omit the second specifier, th=
en the
> first one applies to getting and setting, as now. If you include it, the
> first one applies to getting, the second one to setting.
>
> It=E2=80=99d also be compatible with properties, too:
>
>     public/private $foobar {
>         get { return $this->bar * $this->foo; }
>         set($value) { $this->bar =3D $value / $this->foo; }
>     }
>
>
Sorry, but I don't like this. This means that the visibility modifier is no
longer next to the thing that it applies to, IMO this is actually harmful
to the readability because the order in which the accessors were defined
then becomes significant so you have to either look at the ordering or have
the parser enforce a particular order, plus "public/private" looks
syntactically weird.

I would suggest something like this:

public $foobar {
    get { return $this->bar * $this->foo; }
    private set($value) { $this->bar =3D $value / $this->foo }
}

...where only a single visibility modifier is permitted on the left, and
this is treated as the *default* visibility for the accessors, which are
free to declare another visibility if they want - so the following would be
equivalent:

public $foobar {
    public get { return $this->bar * $this->foo; }
    private set($value) { $this->bar =3D $value / $this->foo }
}

Another bonus here is that the var keyword can still be permitted on the
left for those who prefer the C# syntax, as a synonym of public (i.e. the
current behaviour of var).

It doesn=E2=80=99t prevent truly read-only properties, either:
>
>     public $foobar {
>         get { return $this->bar * $this->foo; }
>     }
>
> Does this sound like a good idea? A similar idea came up in the
> discussions 8 years ago on readonly.
>
> --
> Andrea Faulds
> http://ajf.me/
>
>
>
>
>
> --
> PHP Internals - PHP Runtime Development Mailing List
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>
>

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