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Date: Sat, 19 Nov 2016 20:22:36 +0100
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To: Larry Garfield <larry@garfieldtech.com>
Cc: PHP Internals List <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Immutability RFC
From: michal.brzuchalski@gmail.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=)

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19.11.2016 19:15 "Larry Garfield" <larry@garfieldtech.com> napisa=C5=82(a):
>
> I'm not Paul, but...
>
> If you have a data storage system using CRAP (Create Read Archive Purge)
instead of CRUD, or EventSourcing, or any other system that needs to
maintain history, then you need stored objects that have identities
(document abc revision 123, for instance) so you can reference them.  In
order to maintain history, however, when you load that data into a classed
object you do NOT want that object to be mutable, because there is, by
design, no way to "update" that object in place in storage.  Rather, you'd
want to have a special "new object" class that is mutable, persist that to
storage, and then on load of historical data you want a read-only object to
expose to application code.  That object will still have an identity,
however.
>

In Event Sourced application Aggregates and Entities are mutable but
pushing Events for later write but speaking of ValueObject which ideally
could be immutable classes there is must on immutability and AFAIK there is
no need for identity for them. Am I right?

> I'm actually working on such a library on the side right now.
>
> --Larry Garfield
>
>
> On 11/16/2016 11:57 AM, Silvio Mariji=C4=87 wrote:
>>
>> @Paul,
>> I understand that immutable doesn't automatically apply value object. Ca=
n
>> you give us some examples where immutable object should have identity?
>>
>> Cheers
>> On Nov 16, 2016 4:48 PM, "Paul Jones" <pmjones88@gmail.com> wrote:
>>
>>>> On Nov 16, 2016, at 07:57, Silvio Mariji=C4=87 <marijic.silvio@gmail.c=
om>
>>>
>>> wrote:
>>>>
>>>> Hi,
>>>>
>>>> To anyone who is interested in this RFC. What do you think what
behavour
>>>
>>> we
>>>>
>>>> should have when you try to compare two immutable objects by identity
>>>
>>> like
>>>>
>>>> this:
>>>
>>> I don't mean to be overly-nitpicky here, but it strikes me that the
issue
>>> might not be "immutable object" so much as "value object."
>>>
>>> That is, an immutable object (or at least a read-only object) might ver=
y
>>> well have an identity.  But a *value* object, in addition to read-only
or
>>> immutable, would have no identity proper.
>>>
>>> Maybe using the alternative term (if it applies) would help to clarify
the
>>> situation.
>>>
>>>
>>> --
>>> Paul M. Jones
>>> pmjones88@gmail.com
>>> http://paul-m-jones.com
>>>
>>> Modernizing Legacy Applications in PHP
>>> https://leanpub.com/mlaphp
>>>
>>> Solving the N+1 Problem in PHP
>>> https://leanpub.com/sn1php
>>>
>>>
>>>
>>>
>
>
> --
> PHP Internals - PHP Runtime Development Mailing List
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