Dart News & Updates

Three weeks ago , I wrote about the stream_channel package. Two weeks ago , I wrote about the json_rpc_2 package which is built on top of stream_channel . This week I’ll complete the trifecta by writing about the vm_service_client package, which uses json_rpc_2 in turn—and is a really cool package in its own right! One of the lesser-known corners of the Dart VM is its service protocol , but it’s one of its most powerful components. It uses JSON-RPC 2.0 over WebSockets to allow clients to connect to the VM, inspect its internal state, set breakpoints, and all sorts of neat stuff. If you’ve ever used Observatory for debugging or profiling your Dart code, you’ve been using the service protocol under the hood: that’s how the Observatory web app talks to the VM’s internals. Because the protocol is fully documented and based on a standard underlying protocol, it’s possible for anyone to use from their code. And the vm_service_client package makes it downright easy: it provides a Da...

Last week I wrote about the stream_channel package for two-way communication, so this week it seemed natural to move to a package that uses it: json_rpc_2 . This is an implementation of the JSON-RPC 2.0 specification, which is a popular protocol for providing structure and standardization to WebSocket APIs. Although it’s most commonly used with WebSockets, the protocol itself is explicitly independent of the underlying transport mechanism. This makes it a great fit for stream channels, which can be used to represent a two-way stream of JSON objects in a way that works with any underlying mechanism. Thanks to stream channels, JSON-RPC 2.0 can be used across WebSockets , isolates , or any channel a user chooses to wrap. Shared APIs There are three main classes in json_rpc_2 : Client makes requests and receives responses, Server handles requests and returns responses, and Peer does both at once. Because all of these involve two-way communication, they all have the same two ...

Nane Kratzke is a professor of Computer Science at the Lübeck University of Applied Sciences  in North Germany. He conducts cloud computing research at the university’s Center of Excellence for Communications, Systems, and Applications (CoSA). He also gives Computer Science courses — one of which uses Dart as a vehicle to teach web programming. We asked Nane about this.   [Off-topic] Is it true you were researching network warfare at some point in your past? Yes, that is true. I was enlisted in German Navy as a Navy Officer and during my military time I studied Computer Science at the University of Federal Armed Forces in Munich, Germany. For about six years after my studies, I was involved as a software engineer, team leader and project leader in several programs for command and control systems of German frigates. After that, I worked as a consulting software architect for a German think tank consulting mainly the German Ministry of Defence. I did some research...

Dart 1.16 is now available . This release includes important updates to our tools. Faster developer tools In this release, we've been working closely with our users at Google to make sure Dart is even more productive for developers. We've optimized how Dartium loads applications, improving the time it takes to open an application up to 40%. We also continue to invest in faster code analysis and quicker JavaScript compile times. You should see improved performance in this and future releases. Updated HTML APIs In Dart 1.15 we updated Dartium to Chrome 45 from Chrome 39. In this release, we've updated our browser APIs – dart:html, dart:svg, etc. – to align with these changes. While most of these changes involve new and lesser used APIs, you should verify your application code to find and fix possible breaks. And more... The SDK changelog has details about all of the updates in Dart 1.16 SDK. Get it now .

The stream_channel package is the youngest I’ve written about so far—the first version was published on 28 January 2016, only three months ago as I write this! But despite its youth, it fills a very important role in the Dart ecosystem by providing a common abstraction for two-way communication. In my article on source_span , I wrote about how important it is for a package ecosystem to provide common conventions that can be used throughout the language. stream_channel is another great example of that. The core API it provides is extremely simple, just two getters and a set of rules for them to follow, but the ability for Dart code to implement protocols independent of the underlying implementation is profound. abstract class StreamChannel < T > { Stream < T > get stream ; StreamSink < T > get sink ; } The test package uses StreamChannel to implement a protocol for running tests that works whether the tests are in an isolate, a separate proce...

We’ve covered individual values and we’ve covered streams , but there are still a few more goodies available in the async package. These don’t fit neatly in either bucket, but when you run into situations that call for them, they’re still plenty useful. Wrappers Just like the collection package , async provides a set of wrapper classes. Each of these classes implements a dart:async class and forwards all calls to an inner instance of that class. This makes it easy for users to provide customized versions of those classes. In fact, the async package itself uses some of its own wrappers. There’s a DelegatingFuture class, of course. There’s also a DelegatingStreamSubscription , and wrappers for every kind of sink or consumer you can name: DelegatingSink , DelegatingEventSink , DelegatingStreamConsumer , and of course DelegatingStreamSink . Of these, DelegatingStreamSink is used most often since it encompasses all the functionality of the other classes. /// A [StreamSin...