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Decorator classes

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Mathieu Rochette

9 years ago

Hello internals,

I find that using the decorator pattern is very verbose and maybe
something could be done about that,
an article[1] I saw proposed a "decorates" keyword to solves this, here
is how it might look like in PHP:

interface Foo {
public bar();
public taz();
}

class EchoFooBar decorates Foo {
public function bar() {
$this->logger->debug("foo bar");
return $this->decorated->bar();
}
}

class LoggedFooTaz decorates Foo {
private $logger;

public function __construct(Foo $decorated, Logger $logger) {
$this->logger = $logger;
$this->decorated = $decorated;
}

public function taz() {
$this->logger->debug("foo taz");
return $this->decorated->taz();
}
}

* the constructor is optional and default to take the first argument and
put it in $decorated
* if the constructor is provided PHP check that $decorated is set and
implements the decorated interface or class
* all public methods not overridden are automatically proxied to the
decorated object

There is at least a few different ways to go about this, the previous
example was just to give you a preview of what it could be. If there is
interest I'd like to write an RFC for this :)

What do you think about this ?


thank you


[1] https://dzone.com/articles/is-inheritance-dead

Marco Pivetta

9 years ago

On Thu, Dec 29, 2016 at 2:12 PM, Mathieu Rochette <mathieu@rochette.cc>
wrote:

> Hello internals,
>
> I find that using the decorator pattern is very verbose and maybe
> something could be done about that,
> an article[1] I saw proposed a "decorates" keyword to solves this, here is
> how it might look like in PHP:
>
> interface Foo {
>   public bar();
>   public taz();
> }
>
> class EchoFooBar decorates Foo {
>   public function bar() {
>     $this->logger->debug("foo bar");
>     return $this->decorated->bar();
>   }
> }
>
> class LoggedFooTaz decorates Foo {
>   private $logger;
>
>   public function __construct(Foo $decorated, Logger $logger) {
>     $this->logger = $logger;
>     $this->decorated = $decorated;
>   }
>
>   public function taz() {
>     $this->logger->debug("foo taz");
>     return $this->decorated->taz();
>   }
> }
>
> * the constructor is optional and default to take the first argument and
> put it in $decorated
> * if the constructor is provided PHP check that $decorated is set and
> implements the decorated interface or class
> * all public methods not overridden are automatically proxied to the
> decorated object
>
> There is at least a few different ways to go about this, the previous
> example was just to give you a preview of what it could be. If there is
> interest I'd like to write an RFC for this :)
>
> What do you think about this ?
>
>
> thank you
>
>
> [1] https://dzone.com/articles/is-inheritance-dead
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>

Just my 2 cents:

Too much magic syntactic sugar, whereas you are just saving very little
time while implementing a few method stubs that take..

Yet, in order to achieve that, you added a huge amount of complexity for
all the tooling that  relies on the AST, including PHP itself.
.
Marco Pivetta

http://twitter.com/Ocramius

http://ocramius.github.com/

Mathieu Rochette

9 years ago

On 29/12/2016 14:18, Marco Pivetta wrote:

>
> On Thu, Dec 29, 2016 at 2:12 PM, Mathieu Rochette <mathieu@rochette.cc
> <mailto:mathieu@rochette.cc>> wrote:
>
>     Hello internals,
>
>     I find that using the decorator pattern is very verbose and maybe
>     something could be done about that,
>     an article[1] I saw proposed a "decorates" keyword to solves this,
>     here is how it might look like in PHP:
>
>     interface Foo {
>       public bar();
>       public taz();
>     }
>
>     class EchoFooBar decorates Foo {
>       public function bar() {
>         $this->logger->debug("foo bar");
>         return $this->decorated->bar();
>       }
>     }
>
>     class LoggedFooTaz decorates Foo {
>       private $logger;
>
>       public function __construct(Foo $decorated, Logger $logger) {
>         $this->logger = $logger;
>         $this->decorated = $decorated;
>       }
>
>       public function taz() {
>         $this->logger->debug("foo taz");
>         return $this->decorated->taz();
>       }
>     }
>
>     * the constructor is optional and default to take the first
>     argument and put it in $decorated
>     * if the constructor is provided PHP check that $decorated is set
>     and implements the decorated interface or class
>     * all public methods not overridden are automatically proxied to
>     the decorated object
>
>     There is at least a few different ways to go about this, the
>     previous example was just to give you a preview of what it could
>     be. If there is interest I'd like to write an RFC for this :)
>
>     What do you think about this ?
>
>
>     thank you
>
>
>     [1] https://dzone.com/articles/is-inheritance-dead
>     <https://dzone.com/articles/is-inheritance-dead>
>
>     --
>     PHP Internals - PHP Runtime Development Mailing List
>     To unsubscribe, visit: http://www.php.net/unsub.php
>
>
> Just my 2 cents:
>
> Too much magic syntactic sugar, whereas you are just saving very
> little time while implementing a few method stubs that take..

yeah it's mostly syntactic sugar, I think it would encourage developer
to use this pattern instead of inheritance when appropriate.
I also think that most of the time using the decorator pattern helps
following the single responsibility principle

also, this would add one more benefit : methods that are not override
could probably be optimized by the PHP engine (avoid one userland proxy
call)

Marco Pivetta

9 years ago

On Thu, Dec 29, 2016 at 3:27 PM, Mathieu Rochette <mathieu@rochette.cc>
wrote:

> yeah it's mostly syntactic sugar, I think it would encourage developer to
> use this pattern instead of inheritance when appropriate.
> I also think that most of the time using the decorator pattern helps
> following the single responsibility principle
>

Meh, just `final` as much as possible, combined with interfaces :-)

> also, this would add one more benefit : methods that are not override
> could probably be optimized by the PHP engine (avoid one userland proxy
> call)
>

That's probably something that opcache could do anyway.

Marco Pivetta

http://twitter.com/Ocramius

http://ocramius.github.com/

Alexander Lissachenko

9 years ago

2016-12-29 16:12 GMT+03:00 Mathieu Rochette <mathieu@rochette.cc>:

> I find that using the decorator pattern is very verbose and maybe
> something could be done about that,
> an article[1] I saw proposed a "decorates" keyword to solves this, here is
> how it might look like in PHP:
>

> * the constructor is optional and default to take the first argument and
> put it in $decorated
> * if the constructor is provided PHP check that $decorated is set and
> implements the decorated interface or class
> * all public methods not overridden are automatically proxied to the
> decorated object
>
> There is at least a few different ways to go about this, the previous
> example was just to give you a preview of what it could be. If there is
> interest I'd like to write an RFC for this :)
>
> What do you think about this ?
>

Hi! I think that language doesn't need any additional keywords for that.
What you describe is pure class inheritance and it's already available in
the language.

To be honest I use class inheritance in Go! AOP to define decorators
because of some nice features:

1. No overhead for calling non-decorated method (we can wrap only
required methods)
2. Only one single instance of class, whereas traditional proxy and
decorator pattern will use two instances (one for the original instance
itself and one more instance for proxy/decorator)

What your want can be implemented with the help of one single aspect,
applied to your codebase. Then framework will automatically create
decorators for every required class in your system. For logging decorator
example see my blogpost here:
http://go.aopphp.com/blog/2013/07/21/implementing-logging-aspect-with-doctrine-annotations/

Mathieu Rochette

9 years ago

On 29/12/2016 14:44, Alexander Lisachenko wrote:

>
> 2016-12-29 16:12 GMT+03:00 Mathieu Rochette <mathieu@rochette.cc
> <mailto:mathieu@rochette.cc>>:
>
>     I find that using the decorator pattern is very verbose and maybe
>     something could be done about that,
>     an article[1] I saw proposed a "decorates" keyword to solves this,
>     here is how it might look like in PHP:
>
>
>     * the constructor is optional and default to take the first
>     argument and put it in $decorated
>     * if the constructor is provided PHP check that $decorated is set
>     and implements the decorated interface or class
>     * all public methods not overridden are automatically proxied to
>     the decorated object
>
>     There is at least a few different ways to go about this, the
>     previous example was just to give you a preview of what it could
>     be. If there is interest I'd like to write an RFC for this :)
>
>     What do you think about this ?
>
>
> Hi! I think that language doesn't need any additional keywords for
> that. What you describe is pure class inheritance and it's already
> available in the language.

It is not class inheritance, as you can see in my example, the decorator
is on an interface. one point of the decorator pattern is that you don't
need to know
which class (or subclass) you are decorating. any object implementing
the interface (or extending the class if it's a class you are
decorating) can be decorated.

>
> To be honest I use class inheritance in Go! AOP to define decorators
> because of some nice features:
>
>  1. No overhead for calling non-decorated method (we can wrap only
>     required methods)
>

I think PHP could be smart enough to do that too for non-decorated
methods with the decorates keyword

>
>  1. Only one single instance of class, whereas traditional proxy and
>     decorator pattern will use two instances (one for the original
>     instance itself and one more instance for proxy/decorator)
>

I'm not sure decorator is appropriate here, in the article you are not
decorating[1] your class; you are outsourcing the behavior but it's not
the same

>
> What your want can be implemented with the help of one single aspect,
> applied to your codebase. Then framework will automatically create
> decorators for every required class in your system. For logging
> decorator example see my blogpost here:
> http://go.aopphp.com/blog/2013/07/21/implementing-logging-aspect-with-doctrine-annotations/
>

[1] https://en.wikipedia.org/wiki/Decorator_pattern