Thank you for your feedback.
I am already using a solution like the one
proposed by Robert: it works but it
leaves some doubts since each project
can have a different name for NotSet
while it seems a general concept of the
language.
Besides the example I proposed, I think
that there are many cases where you
can check if the property is initialised
or not and for consistency "null" should
be considered a valid initialization value.
Are there any downsides in adding a
specific syntax to check if a property
is initialized with any value?
Thank you.
Luigi Cardamone
Backend developer
Italy
Il Sab 18 Mag 2024, 11:19 Robert Landers <landers.rob...@gmail.com> ha
scritto:
> On Fri, May 17, 2024 at 11:43 PM Luigi Cardamone
> <cardamonelu...@gmail.com> wrote:
> >
> > Hello Internals,
> > during last PHPDay in Verona I discussed this topic with some of
> > you and it was suggested to me to send an email here.
> >
> > Here is an example to describe my problem. Imagine a simple
> > DTO like this:
> >
> > class MyDTO{
> > public ?int $propA;
> > public ?int $propB;
> > }
> >
> > Imagine that a Form processor or a generic mapper fill some of
> > these fields with a null value:
> >
> > $dto = new MyDTO();
> > $dto->propA = null;
> >
> > Sometimes we use DTOs to handle PATCH requests and not all
> > the properties are mapped with a value. In a scenario like this,
> > "null" is often a valid value.
> >
> > At this point, I need a way to find if a property was initialized or
> > not but unfortunately "isset" is not a solution. When I write:
> >
> > echo isset($dto->propA) ? 'init' : 'not-init';
> >
> > I get "not-init" since isset returns true only if the variable is set
> > and different from null.
> >
> > Full example: https://3v4l.org/4cCj0
> >
> > Is the language missing a clean way to check if a property is
> > initialized or not? Is there any solution to this problem?
> >
> > The only alternative is using reflection but I need to pass the
> > property name as a string losing static analysis.
> > Proposing a new language syntax like
> > "is_initialized($dto->propA)" can be an interesting solution?
> >
> > Thank you in advance.
> >
> > Luigi Cardamone
> > Backend developer
> > Italy
>
> I wouldn't rely on checking initialized or not. Instead, use a sentinel
> value:
>
> class NotSet {}
>
> define("NotSet", new NotSet());
>
> class MyAwesomeValue {
> public NotSet|null|string $aValue = NotSet;
> }
>
> This way, even programmers can "unset" a property by simply setting
> $value->aValue = NotSet without having to rely on the weird PHP
> semantics of unsetting a property. You can also use this to
> declaratively encode which properties cannot be unset, without having
> to define it in your mapping code.
>
> Robert Landers
> Software Engineer
> Utrecht NL
>
