On Tue, 17 Nov 2015, 02:07 Andrea Faulds <a...@ajf.me> wrote: Hi,
Chris Riley wrote: > > There has been a lot of interest recently (eg psr-7) in immutable data. I'm > considering putting an RFC together to add language support for immutables: > I wonder if immutable classes are really the right way to go. Immutable reference types with manual copying are somewhat alien to PHP: instead, the language has used copy-on-write mutable value types for arrays and strings, and prior to PHP 5, objects. Copy-on-write value types have all the benefits immutable types do. They can't be mutated at a distance unless you make a reference to them, trees made of them can be compared for equality with just ===, etc. But they also have benefits that immutable types lack. They're easier to work with, because you can directly mutate them like everyone's used to doing: no messing around with withFooBar() and withoutFooBar(), you just set foobar or remove it directly. And PHP handles the duplication of objects for you implicitly, so there's far less code to write. Unfortunately, PHP 5 got rid of PHP 4's value type objects and replaced them with reference type objects. But we could always introduce a way to get value type objects again. How about a `struct` keyword? It would be equivalent to `class`, but produce a value type rather than a reference type. Any thoughts? Thanks. -- Andrea Faulds http:// <http://ajf.me/>ajf.me/ <http://ajf.me/> -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http:// <http://www.php.net/unsub.php>www.php.net <http://www.php.net/unsub.php>/ <http://www.php.net/unsub.php>unsub.php <http://www.php.net/unsub.php> My main motivation for this was for event objects when doing event sourcing - they are by definition unchangeable after creation. That said, considering the wider use case there does seem to be a need to emulate the with* functions. One option would be to hide the messy constructor call within user defined methods, but that would add a lot of boilerplate - something I was wanting to reduce not increase. I can't think of a clean easy way to add with* functionality at a language level without even more magic (parameter skipping?) As for setter injection - my initial proposal would support that - a property declared immutable allows itself to be set - once. If someone can give my wiki account rfc karma I can write this up so far too help focus discussion. ~C
