Re: [RFC] Immutable variables and objects

Hi Alexander, > On 30 Jan 2015, at 13:07, Alexander Lisachenko <lisachenko.it@gmail.com> wrote: > > Hello, internals! > > Today I was looking at PSR-7 and discovered this part of code: > > $body = new StringStream(json_encode(['tasks' => [ > 'Code', > 'Coffee', > ]]));; > $request = $baseRequest > ->withUri($uri->withPath('/tasks/user/' . $userId)) > ->withMethod('POST') > ->withHeader('Content-Type' => 'application/json') > ->withBody($body); > $response = $client->send($request); > > What is wrong here? Emulated immutability. All methods will create a > separate instance of request, so > $baseRequest->withUri()->withMethod()->withHeader()->withBody() will create > total 5 object instances. It's a memory overhead and time consumption for > each method call. Yes, I also think this is unfortunate. > What I want to discuss is true immutability flag for variables and > parameters. There are a lot of languages that use "final" or "const" > keywords to prevent modification of variables. We can use this approach by > extending language syntax as following: This approach wouldn’t solve the problem you’re describing. You *still* need to produce a new request object, because the request object is immutable. The mutability of its *properties* isn’t the issue. If you want to avoid creating five different objects, you’d need to implement value-type objects that are passed by value and use copy-on-write. Basically, you’d need to re-add PHP 4 style classes. Thanks. -- Andrea Faulds http://ajf.me/