Constructor parent property promotion

php.internals

Mathieu Rochette

6 years ago
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

Lokrain

6 years ago
On Mon, 17 Aug 2020 at 19:46, 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,
Why do you use visibility modifier inside here?
> > > parent string $name, > > ) {
C# has something like this ) : base($name)

Mathieu Rochette

6 years ago
    "Lokrain" lokrain@gmail.com – August 17, 2020 7:14 PM  
>   > > On Mon, 17 Aug 2020 at 19:46, 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, > > Why do you use visibility modifier inside here?
This the new PHP 8 feature brought by the Constructor Property Promotion RFC: https://wiki.php.net/rfc/constructor_promotion
>>        parent string $name, >> >>    ) { > > C# has something like this ) : base($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

Mathieu Rochette

6 years ago
On 8/17/20 7:14 PM, Lokrain wrote:
> > > On Mon, 17 Aug 2020 at 19:46, 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, > > Why do you use visibility modifier inside here?
This the new PHP 8 feature brought by the Constructor Property Promotion RFC: https://wiki.php.net/rfc/constructor_promotion <https://wiki.php.net/rfc/constructor_promotion>
> > >        parent string $name, > >    ) { > > C# has something like this ) : base($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

Andreas Hennings

6 years ago
Interesting stuff! https://wiki.php.net/rfc/constructor_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. Does it map to parent constructor parameters, or to parent properties? -> I assume to parent constructor parameters, because parent properties could be private. Can the 'parent' parameters be intermixed with other parameters? -> I assume yes, not allowing it would be an unnecessary limitation. 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: