Proposal fo "Code-free constructors declaration" View as Markdown

Proposed syntax
class A($prop) extends B("BlaBla", $prop) {
}

Would this work with anonymous classes? If so, how would the syntax look
like?

Currently this syntax can't be used with anonymous classes because those
classes instantiated
at once they declared and same syntax is used for forwarding parameters
directly into constructor.

new class(10) extends SomeClass implements SomeInterface {
public function __construct($num) {...}
}

I think that it is possible to create additional rule when use
"parameter_list" instead of "argument_list".
Some research is required.
But it will add some ambiguity when reading code.

Proposed syntax
class A($prop) extends B("BlaBla", $prop) {
}

Would this work with anonymous classes? If so, how would the syntax look like?

I have the same question. I don't think it would work with them, but I
could be wrong.

I'm added an illustration. Maybe it more clear for understanding.
https://wiki.php.net/_detail/rfc/joined.png?id=rfc%3Acode_free_constructor

Proposed syntax
class A($prop) extends B("BlaBla", $prop) {
}

This looks like unobvious magic. PHP approach has traditionally been to
avoid unobvious magic, and be explicit about what is happening.
This functionality does not seem no be enabling anything different,
and seems to be pretty obscure as to what is going on.
There is no magic, just alternative constructor syntax with some
default behavior. Additional paragraph in documentation will resolve
all obscurity.

Vice versa, this syntax make behavior more strict. No need to
read constructor's body, because you know exactly what's going on.

Also there is no place for typos in boilerplate and refactoring errors.

IMHO inheritance also is more clear, because no need to search
"parent::__construct" in the middle of class body.

Also, $prop can not be documented this way, and assigning default
value to it may be a bit weird too.
Not sure that I understand this remark right way. What did you mean?
You can use php-doc similar you used it for functions.
Parameters block identical to function parameters block,
including types and default values.

I am all for paving the walkways, but this particular case
seems to be a bit too narrow to have a special language syntax for, and
the syntax seems to be not exactly obvious as to what's going on there.
Matter of quality of documentation.

To Levi Morrison and Bruce Weirdan.

Would this work with anonymous classes? If so, how would the syntax
look like?
I have the same question. I don't think it would work with them, but I
could be wrong.

There is no big problem to add same functionality to anonymous classes.
But unfortunately only possible syntax(I think) is not very nice.

new class(string $a, int $b, int $c=15)("Hi!", 20) extends SomeClass($a,
115){...}

On Wed, Jan 23, 2019 at 1:33 PM Andrey O Gromov AGromov@alfabank.ru
wrote:

Full description
https://wiki.php.net/rfc/code_free_constructor
Draft realisation
https://github.com/php/php-src/compare/master...rjhdby:constructor

"Code free" constructor is constructor with only purpose to directly set
object properties from received parameters and, optionally, call parent
constructor.

Main idea is to move such constructor declaration inside class
declaration.

Simple example:

Current syntax
class A extends B{
public $prop;

public function __construct($prop){
    parent::__construct("BlaBla", $prop);
    $this->prop = $prop;
}

}

Proposed syntax
class A($prop) extends B("BlaBla", $prop) {
}

With respect, Andrey.

Two alternatives you might want to consider:

• https://wiki.php.net/rfc/automatic_property_initialization => Proposed
  function public function __construct(int $this->x, int $this->y) {}, which
  avoids the need for explicit property assignments in the ctor. However, the
  property still needs to be declared separately.

https://docs.hhvm.com/hack/other-features/constructor-parameter-promotion
=> Uses public function __construct(public int $x, public int $y) {} to
declare properties in-line in the constructor.

I think that if we want to add some kind of sugar of this type, then I'd
strongly prefer the syntax used by Hack than the one proposed here. It
makes a lot more sense to me intuitively, probably because the property
declarations still looks like normal property declarations, they just occur
in-line in the ctor.

Nikita

To add to this: While I can totally understand the motivation to avoid the
property/constructor boilerplate (where the property name needs to be
repeated four times), I think that this is really solving the wrong
problem. The problem is the need to have a constructor at all.

Both this RFC and the two alternatives mentioned above really target the
case of "dumb" constructors that don't really do anything beyond assigning
properties from ctor arguments. I think that that is better solved by
adding a first-class syntax for object construction. I have something
roughly like this in mind:

class Point {
public int $x;
public int $y;
public int $z;
}

// (syntax just a dummy)
$origin = new Point { x = 0, y = 0, z = 0 };

Where the object initialization syntax ensures that all properties that
don't have defaults are initialized. Especially now that we have typed
properties and it is feasible to have data objects with just public typed
properties, I think that this is the way to avoid ctor boilerplate, rather
than making it simpler to write that boilerplate.

Nikita

Am 25.01.2019 um 11:44 schrieb Nikita Popov:

I think that if we want to add some kind of sugar of this type, then I'd
strongly prefer the syntax used by Hack than the one proposed here.

Agreed.