Warning: We expect the Dart libraries to undergo potentially sweeping changes before Dart goes to alpha. This document is relevant as of 2011-12-22.
Dart is a "batteries included" effort to help app developers build modern web apps. An important "battery" is the bundled core Dart libraries, providing common and rich functionality. Dart is building a solution for large, complex web apps, and providing well tested, integrated, and common libraries is key to helping a web app developer be more productive out of the box.
The Collection libraries are a crucial set of APIs that Dart developers get for free. Much more than simple arrays and maps, the Collection library includes standard ways to filter, iterate, inspect, compose, and sort your data. This post specifically looks at List<E>, Dart's ordered, indexable collection of objects.
Three new language features just landed in the latest dev channel build of the Dart! Collectively known as null-aware operators, these new features will help you reduce the code required to work with potentially null objects.
I'm excited for these new abilities, because typing less is always a good thing. Read on to learn more, and be sure to try these new features on Dart Pad.
Use ?? when you want to evaluate and return an expression IFF another expression resolves to null.
exp ?? otherExp
is similar to
((x) => x == null ? otherExp : x)(exp)
Use ??= when you want to assign a value to an object IFF that object is null. Otherwise, return the object.
obj ??= value
is similar to
((x) => x == null ? obj = value : x)(obj)
Use ?. when you want to call a method/getter on an object IFF that object is not null (otherwise, return null).
is similar to
((x) => x == null ? null : x.method())(obj)
You can chain ?. calls, for example:
Warning: We expect the Dart libraries to undergo potentially sweeping changes before Dart goes to alpha. This document is relevant as of 2012-01-02.
Dart is not just a language, but a full "batteries included" effort to create a productive, familiar, and fun environment for the modern web app developer. The bundled libraries are one such "battery", including many common classes and utilities such as date manipulation, regular expressions, even asynchronous constructs like Future and Promise.
Probably the most used set of libraries will be the Collections, such as List, Map, and Set. In this post, we'll take a look at Map, which is a mapping of keys to values.
In Dart, a Map is an interface designed to manipulate a collection of keys which point to values. Maps can have null values, and can have parameterized types. Note, Maps do not subclass the Collection interfa…