Skip to main content

Dart Lang meeting: All objects hashable, and more

Posted by Bob Nystrom


Here's my notes from this week's Dart language meeting:


Getters and implicit "abstract"

Peter raised an interesting corner case with the new getter syntax and the
optional "abstract" keyword. Given this:

  class Foo {
    get bar;
  }

Does it define an abstract getter "bar" whose type is Dynamic, or a field "bar" whose type is "get"?

Gilad says the grammar isn't actually ambiguous here, so there's no problem. (get bar always defines an abstract getter because the spec disallows "get" as a type name.)

We discussed whether "abstract" should be optional or simply removed. Gilad says we should leave it optional in case people want to use it for emphasis. He also wonders if there's a case we aren't thinking of (maybe like the above?) where having it would be helpful to make something clear.

All objects hashable

This is coming in M1. (Woo!) It's just a matter of implementation. We want this in particular so that closures are hashable.

Doc comments

Lars wants to have the language specify the doc comment syntax so that things like the Editor can parse it. The plan is to go through our existing comments and see what subset of markdown we are actually using in practice and then specify that.

We also would like a doc comment form that works for single-line docs. With lots of short members, it's annoying to have to do:

  /**
   * Tiny comment.
   */
  void tinyMember() => 'blah';

I pointed out that I already borrowed "///" from C# and added support for it in Dartdoc, so they said we'll go with that.

Streaming string interpolation

Lars brought up an issue that he wonders if we'll want language support for at some point. The problem comes when you're getting some recursive structure and stringifying it to a stream. If you use interpolation in that, you can end up back at n^2 complexity.

Should we look into some kind of streaming support for string interpolation? No resolution yet.

Cheers!

Comments

Popular posts from this blog

Const, Static, Final, Oh my!

Posted by Seth Ladd

(This is an "oldie but a goodie" misc@dartlang.org post originally written by Bob Nystrom. It is being posted here as the explanations still ring true.)

Bob writes:


"static", "final", and "const" mean entirely distinct things in Dart:

"static" means a member is available on the class itself instead of on instances of the class. That's all it means, and it isn't used for anything else. static modifies *members*.

"final" means single-assignment: a final variable or field *must* have an initializer. Once assigned a value, a final variable's value cannot be changed. final modifies *variables*.

"const" has a meaning that's a bit more complex and subtle in Dart. const modifies *values*. You can use it when creating collections, like const [1, 2, 3], and when constructing objects (instead of new) like const Point(2, 3). Here, const means that the object's entire deep state can be determ…

Dart 1.12 Released, with Null-Aware Operators and more

Dart 1.12.0 is now released! It contains the new null-aware operators language feature, and enhancements to pub, Observatory, dartdoc, and much more.

Null-aware operators

The new null-aware operators help you reduce the amount of code required to work with references that are potentially null. This feature is a collection of syntactic sugar for traversing (potentially null) object calls, conditionally setting a variable, and evaluating two (potentially null) expressions.

Click or tap the red Run button below to see them in action.

??

  if null operator. `expr1 ?? expr2` evaluates to `expr1` if not `null`, otherwise `expr2`.


??=

  null-aware assignment. `v ??= expr` causes `v` to be assigned `expr` only if `v` is `null`.

x?.p

  null-aware access. `x?.p` evaluates to `x.p` if `x` is not `null`, otherwise evaluates to `null`.

x?.m()

  null-aware method invocation. `x?.m()` invokes `m` only if `x` is not `null`.

Learn more about Dart's null-aware operators in our Language Tour.

.packages fi…

The new AdWords UI uses Dart — we asked why

Google just announced a re-designed AdWords experience. In case you’re not familiar with AdWords: businesses use it to advertise on google.com and partner websites. Advertising makes up majority of Google’s revenue, so when Google decides to completely redo the customer-facing front end to it, it’s a big deal. The Dart team is proud to say that this new front end is built with Dart and Angular 2. Whenever you asked us whether Google is ‘even using Dart for anything,’ this is what we had in mind but couldn’t say aloud. Until now. We asked Joshy Joseph, the primary technical lead on the project, some questions. Joshy is focusing on things like infrastructure, application latency and development velocity, so he’s the right person to ask about Dart.Q: What exactly did we launch on Monday?It’s a complete redesign of the AdWords customer experience that is rolling out slowly as a test to a small initial set of advertisers. The most noticeable thing is probably the Material Design look and f…