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To: Andreas Hennings <andreas@dqxtech.net>
Cc: "PHP internals (internals@lists.php.net)" <internals@lists.php.net>
Message-ID: <086db73b-63a1-0e78-1302-903b3f8c02c3@rochette.cc>
Date: Wed, 2 Sep 2020 02:01:38 +0200
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Subject: Re: [PHP-DEV] Constructor parent property promotion
From: mathieu@rochette.cc (Mathieu Rochette)

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"Andreas Hennings" andreas@dqxtech.net – August 17, 2020 7:19 PM

    Interesting stuff!

    https://wiki.php.net/rfc/constructor_promotion
    <https://cloud.rochette.cc/index.php/apps/mail/redirect?src=https%3A%2F%2Fwiki.php.net%2Frfc%2Fconstructor_promotion>

    I see this for the first time, but I like it :)

    Now to your proposal.

    Just to make sure I understand:
    Would this map the parameters by name or by index?

    -> I assume by index, it makes more sense.

if they are mapped by index it means I can’t benefit from this feature 
without copying all the optional parameters up to the ones I’m 
interested in.

Which will probably be even more widespread in the future thx to the 
Named Paramters RFC: 
https://wiki.php.net/rfc/named_params#object_initialization

So, I was thinking the opposite, if they are mapped by name it means I 
can avoid passing some the optional parameters if’m not interested in 
the first ones

    Does it map to parent constructor parameters, or to parent properties?

    -> I assume to parent constructor parameters, because parent
    properties could be private.

exactly

    Can the 'parent' parameters be intermixed with other parameters?

    -> I assume yes, not allowing it would be an unnecessary limitation.

that was my intent yes

    So if you use the 'parent' syntax, you need exactly as many
    parameters with 'parent' as required by the parent constructor.

    // Parent class

    class B {

       public function __construct($b0, $b1) {

         // The values may or may not be written to properties, it does
    not matter.

       }

    }

    // Child class

    class C extends B {

       public function __construct(parent $x, private $c0, parent $y,
    private $c1) {

         // Implicit: parent::__construct($x, $y);

       }

    }


    On Mon, 17 Aug 2020 at 18:46, Mathieu Rochette <mathieu@rochette.cc>
    wrote:

        Hi,



        I’m writing a message here to receive feedback on a two ideas
        related to
        class constructors before going more in details with an RFC. I
        hope this is
        appropriate behavior for this list



        With the Constructor Property Promotion accepted in PHP 8,
        there’s a lot
        less of boilerplate when writing class constructors. I’m
        suggesting two
        additional ways of making thing even easier and I hope, readable.



        First: I’d like to be able to automatically transfer a constructor
        property to its parent constructor. I’m thinking of something
        like that:



        ```php

        class MyCommand extends Command

        {

            public function __construct(

                private Connection $connection,

                parent string $name,

            ) {

            }

        }

        ```



        This would be the equivalent of :



        ```php

        class MyCommand extends Command

        {

            public function __construct(

                private Connection $connection,

                string $name,

            ) {

                parent::__construct($name);

            }

        }

        ```



        The second idea is to make the constructor body optional, the
        first example
        would now be:



        ```php

        class MyCommand extends Command

        {

            public function __construct(

                private Connection $connection,

                parent string $name,

            )

        }

        ```



        This would call the parent constructor automatically even if no
        "parent"
        parameter are present. I could even see this enforced by linter
        to avoid
        having logic in the constructors.



        If there is interest I’d like to try writing an rfc and
        implement it. I
        have not much knowledge of the php-src code but I hope this is a
        small
        enough change that I’ll be able to tackle. So, at that time if
        someone is
        interested in mentoring this little project I’d appreciate it :)





        regards,



        Mathieu





--
Mathieu Rochette


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