2. This is Dart…
A language
And a tool ecosystem
For creating complex webapps
In teams
Single threaded
But isolates provide "shared-nothing" concurrency
Optionally typed
Runs in a Browser Virtual Machine
Or a Server Virtual Machine
Can be converted to JavaScript
3. Technical Preview…
What you may see today, may change tomorrow…
Enable us (as potential end users) to influence the
language and provide feedback
Eventual goal is standardization
4. Why Dart…
What do Google build?
Single page web-apps Browser
Instant search Apps
Docs
Google Plus Server
Blogger side
Analytics APIs
Maps
… etc …
5. Why Dart?
Complex applications
Team development
Easily “toolable”
//process a & b.
function process(a,b) {
return a+b;
};
document.write(process(1,2,3));
document.write(process("Hello", " World"));
document.write(process({name:'objectA'},
{name:'objectB'}));
6. Why Dart – the alternatives?
GWT
Still around and will be driven by Google's use cases
CoffeeScript
Closer to JavaScript, syntax inspired by Ruby, Python
JavaScript + Framework X
The default option
Dart is not a replacement, but an option.
7. Design Goals - Flexibility
Flexible, but with structure
Optional types provide flexibility
Libraries to organize code
Classes and Interfaces to provide structure
Tools catch errors
8. Design goals - Familiar
Be Familiar
main() {
var anInt = 1;
var aStr = "String";
var anObj = new Object();
var result = doSomething(anInt,aStr,anObj);
}
doSomething(a,b,c) {
return "blah";
}
9. Design goals - Familiar
Be Familiar
void main() {
int anInt = 1;
String aStr = "String";
Object anObj = new Object();
String result = doSomething(anInt,aStr,anObj);
}
String doSomething(int a, String b, Object c) {
return "blah";
}
10. Design Goals - Perfomance
Performance as a feature
Currently not as fast as V8
(But D8 is faster at launch than V8 was at launch)
Converted JS should be as fast as or faster than
equivalent hand written JavaScript.
11. Design goals
Great developer IDE
experience
Dart Dart
Frog
Language VM
Native
Browser
17. A quick tour of some interesting
language features…
18. Dart: Classes and interfaces
Familiar (to Java and C# developers) Optional
But a couple of nice features paramters
class Duck implements Quackable {
var colour;
Duck([this.colour="red"]) { }
Duck.yellow() { Named
this.colour = "yellow"; constructors
}
//Usage
String sayQuack() => "quack";
var duck1 = new Duck();
}
var duck2 = new Duck("blue");
Unsurprising Function var duck3 = new Duck.yellow();
this shorthand print(duck3.sayQuack());
19. Dart: Classes and interfaces
Familiar (to Java and C# developers)
But a couple of nice features
interface Quackable default Duck {
String sayQuack();
}
//Usage
var duck1 = Quackable();
20. Dart: Classes and interfaces
All classes are also interfaces
class Person implements Duck { … }
Class properties can be interchanged with getters and setters
duck.colour = "yellow"; //setter, or property?
class Duck {
var _colour; //private property
get colour() => _colour; //getter
set colour(value) { //setter
_colour=value;
}
}
21. Dart: Libraries and Source
Break up single source code file into multiple,
independent files. #library("myLibrary");
#import("./libs/otherLib.dart");
#source("./myFile1.dart");
#source("./myFile2.dart");
Break logical parts of an app into libraries.
Import your own and third party libraries.
Privacy declarations apply at a library level
(not a class level)
22. Dart: Optional Types
Add documentation to code
Documentation readable by humans and tools
"Innocent until proven guilty"
Types have no effect on the running application
var i = 1; int i = 1;
var s = "Hello"; String s = "Hello";
String i = 1;
int s = "Hello"; Probably wrong, but not
proved to be wrong.
23. Dart: Optional Types
Optional types can be useful in the early days of developing
an app
class Person {
sayQuack(){
return "ouch…quack";
}
}
pokeDuck(duck) {
duck.sayQuack();
}
//Usage
But is that what the
pokeDuck(new Duck());
library designer
pokeDuck(new Person()); //runs fine
intended?
24. Dart: Optional Types
But as you add structure, types can help you…
class Person {
sayQuack(){
return "ouch…quack";
}
}
pokeDuck(duck) {
duck.sayQuack();
duck.swimAway();
}
//Usage
This now fails with a pokeDuck(new Duck());
noSuchMethod pokeDuck(new Person()); //throws exception
exception
25. Dart: Optional Types
Adding type info provides documentation to tools and
humans.
class Person {
sayQuack(){
return "ouch…quack";
}
}
pokeDuck(Duck duck) {
duck.sayQuack();
duck.swimAway();
}
Now the tools can //Usage
provide warnings (or pokeDuck(new Duck());
errors in checked pokeDuck(new Person()); //tools warn
mode).
26. Dart: noSuchMethod
All classes can have a noSuchMethod method
class Person {
sayQuack(){ Similar to ruby's
return "ouch…quack"; method_missing
}
noSuchMethod(name, args) { Side note: Any
if (name == "swimAway") { object can be
throw "I'm not really a duck"; thrown as an
} exception
}
}
27. Dart: Functions
Simple function syntax Different
main() { syntax, same
effect
var myFunc = (a,b) {
return a,b;
}
Functions as
var myFunc = (a,b) => a+b; arguments
myFunc(a,b) => a+b;
doSomething(c,d, myFunc); Anonymous
doSomething(c,d, (a,b) => a+b); function
var result = myFunc(101,202);
} Unsurprising
function call
28. Libraries: Dart:html
Client side library for interacting with the DOM
Uses Dart constructs for DOM manipulation
var foo = elem.query("#foo"); //return a foo
var foos = elem.queryAll(".foo"); //list of foo
Events:
foo.on.click.add((event) {
//do something
});
30. Still a technical preview
Time to get involved…
www.dartlang.org
Join the active mailing list
Search #dartlang on Google +
More still to be built
Reflection!
Libraries providing higher levels of abstraction:
UI frameworks
Server frameworks
