for Java Developers About Me C# since 2005 till 2012 Java since - PowerPoint PPT Presentation

for Java Developers

About Me • C# since 2005 till 2012 • Java since 2012 • JavaScript, Dart since 2013 • Working at Farata Systems • Conduct trainings 2

What is Dart? New programming language and platform created by for Web development 3 3

Blink… � WebKit… Reader… Code Search… Chrome Frame… 4

Dart is Truly OSS • Public commits • Public issue tracker • Public code reviews • Accept contributions 5

• Dart is ECMA standard (TC52) • Also ECMA: JavaScript, C#, C++/CLI, JSON, ActionScript What does it mean? ECMA committee standardizes syntax, semantics, core libraries Why it is important? Safe to develop own VMs and embed in browsers 6

Team • Lars Bak - HotSpot, V8, a Smalltalk VM, BETA • Kasper Lund - HotSpot, V8, OOVM • Gilad Bracha - Java Specification, Strongtalk, Newspeak • Many other engineers 7

http://youtu.be/huawCRlo9H4 8

Timeline Announcement 1.3 Release Sep 1, 2011 Nov 14, 2013 Oct 10, 2011 Apr 9, 2014 First commit 1.0 Release 9

Dart at a glance • Runs in VM • Compiles to JavaScript • Dynamically typed • Object-oriented • Single inheritance • Single-threaded • Familiar sytax 10

How is it better than JS? • Faster • Predictable (no hoisting, no type coercion, etc.) • Rich standard libraries • Structured apps • Good tooling • Packaging system 11

What's Your Benefit? Q: Front-end Developer? Q: Back-end Developer? A: Build reliable apps faster A: Probably just curiosity 12

Language Tour 13


 Hello World • Explicit entry point // Formal example 
 void main(List<String> args) { 
 print( 'Hello from Dart!' ); 
 } 
 // Shorter version 
 main() => print( 'Hello from Dart!' ); 14

Built-in Types var i = 1; 
 int var hex = 0xABCD; var d = 1.2; 
 double var exp = 1.2e9; var s1 = 'single quotes' ; 
 String var s2 = "double quotes" ; var b1 = false ; 
 bool var b2 = true ; var sym1 = #mySymbol; 
 Symbol var sym2 = const Symbol( 'mySymbol' ); List var list = [ 'item1' , 'item2' , 'item3' ]; Map var map = { 'key1' : 'val1' , 2: 'val2' , []: 'val3' }; 15

JSON is valid Dart Syntax • List and Map literals make JSON a valid Dart syntax var map = 
 { 
 'firstName' : 'John' , 
 'lastName' : 'Doe' , 
 'age' : 30, 
 'addresses' : [ 
 { 
 'street' : '' 
 //... 
 }, 
 { 
 'street' : '' 
 //... 
 } 
 ] 
 }; 16

Optional Types Example • Best practice - explicit types for method signatures and class members, for local variables - var main () { void main () { var a = 1; int a = 1; var b = 2; int b = 2; var c = divide(a, b); double c = divide(a, b); assert(c == 0.5); assert(c == 0.5); } } � � divide (a, b) { double divide ( int a, int b) { return a / b; return a / b; } } 17

Optional Types Rules • All type annotations can be omitted • Has no effect at runtime • App without types has the same semantics • Do not cause errors, only warnings • You can always “compile” and run your program 18

Benefits of Type Annotations • Act as documentation • Advanced tools support (completion, code navigation, etc.) • Error detection via type checker • Can improve performance while compiling to JavaScript 19

Declaring Variables • null is default value for all types • Supports final and const var str1 = '' ; // type is dynamic (implicit) 
 String str2 = '' ; // type is String 
 Object str3 = '' ; // type is Object 
 dynamic str4 = '' ; // type is dynamic (explicit) 20


 
 Functions // Top-level functions 
 void log(String message) { 
 print(message); 
 } 
 // Single expression functions 
 void log(String message) => print(message); 
 // Nested functions 
 void main() { 
 void log(String msg) => print(msg); 
 log( 'done' ); 
 } 21


 
 
 Higher-order functions // Accept function as parameter 
 void doSomething(Function callback) { 
 //... 
 callback(); 
 } 
 doSomething(() => log( 'done' )); 
 // Return function 
 Function getLogger() { 
 return (String msg) => log(msg, level: 'INFO' ); 
 } 
 // Assign to a variable 
 var logger = getLogger(); 
 logger( 'done' ); 
 // Define function-type aliases 
 typedef void Logger(String msg); 
 Logger getLogger() { 
 return (String msg) => log(msg, level: 'INFO' ); 
 } 22

Optional Parameters Positional parameters: /// [level] parameter has default value void log(String msg, [Error error, String level = 'INFO' ]) { 
 //... 
 } 
 log( 'Bad value' ); log( 'Bad value' , new ArgumentError()); log( 'Bad value' , new ArgumentError(), ‘ERROR' ); Named parameters: void log(String msg, {Error error, String level}) { 
 //... 
 } 
 log( 'Bad value' ); 
 log( 'Bad value' , level: 'ERROR' ); 
 log( 'Bad value' , level: 'ERROR' , error: new ArgumentError()); 23

Classes 24


 
 
 Class members • Declaratively defined classes and members class WampService { 
 // Instance member 
 WebSocket socket ; 
 // Final member 
 final String id ; 
 // Static member 
 static int buffer_size = 0; 
 // Const member 
 static const String URL = ‘ws://localhost/ws’ ; 
 } 25


 
 
 Getters & Setters class WampService { 
 WebSocket _socket ; 
 get socket => 
 _socket != null ? _socket : _socket = new WebSocket(); 
 set socket(WebSocket s) { 
 if ( _socket .readyState != WebSocket.OPEN) _socket = s; 
 else throw new StateError(); 
 } 
 } 26


 Constructors class Person { 
 String name ; 
 DateTime birthday ; 
 Person(String name, DateTime birthday) { 
 this . name = name; 
 this . birthday = birthday; 
 } 
 } 27


 Automatic Assignment class Person { 
 String name ; 
 DateTime birthday ; 
 Person( this . name , this . birthday ); 
 } 28


 Initializers class Person { 
 String name ; 
 DateTime birthday ; 
 Person(): name = '' , birthday = new DateTime.now(); 
 } 29


 
 
 Named constructors class Collection { 
 //... 
 // Ordinary constructor 
 Collection(List source) {} 
 // Named constructor 
 Collection.empty() {} 
 } 
 var c = new Collection.empty(); 30


 
 
 Factory constructors • Indirect instantiation // Publicly expose abstract class 
 abstract class Service { 
 void doSomething(); 
 // Expose concrete implementation via factory constructor 
 factory Service() => new _DefaultService(); 
 } 
 // Internally provide concrete implementation 
 class _DefaultService implements Service { 
 void doSomething() {} 
 } 
 // You can invoke factory constructors of abstract classes 
 var s = new Service(); 31


 
 
 Factory constructors • Caching pattern class Service { 
 static final Map<String, Service> _cache = {}; 
 String name ; 
 factory Service(String name) => 
 _cache.putIfAbsent(name, () => new Service._(name)); 
 Service._( this . name ); 
 } 32


 
 
 
 
 
 Java: Builder pattern public class User { 
 // Static nested class 
 private String firstName ; // required 
 public static class UserBuilder { 
 private String lastName ; // required 
 private String firstName ; 
 private String phone ; // optional 
 private String lastName ; 
 private int age ; // optional 
 private String phone ; 
 private int age ; 
 � private User(UserBuilder builder) { 
 this . firstName = builder. firstName ; 
 public UserBuilder firstName(String firstName) { 
 this . lastName = builder. lastName ; 
 this . firstName = firstName; 
 this . age = builder. age ; 
 return this ; 
 this . phone = builder. phone ; 
 } 
 } 
 public UserBuilder lastName(String lastName) { 
 this . lastName = lastName; 
 public String getFirstName() { 
 return this ; 
 return firstName ; 
 } 
 } 
 public UserBuilder age( int age) { 
 this . age = age; 
 public String getLastName() { 
 return this ; 
 return lastName ; 
 } 
 } 
 public UserBuilder phone(String phone) { 
 this . phone = phone; 
 public int getAge() { 
 return this ; 
 return age ; 
 } } 
 public User build() { 
 public String getPhone() { 
 return new User( this ); 
 return phone ; 
 } 
 } 
 } 
 // TO BE CONTINUED... } 33


 Dart: a kind of “Builder pattern” class User { 
 String firstName ; 
 String lastName ; 
 String phone ; 
 int age ; 
 // Here "this" enables type checking. 
 User({ this . firstName , this . lastName , this . phone , this . age }); 
 } 
 // Usage 
 var user = new User( 
 firstName: 'John' , 
 lastName: 'Doe' , 
 phone: '+123456789' , 
 age: 30); 34


 
 Cascade operator // Equivalent declaration 
 class User { 
 String firstName ; 
 String lastName ; 
 String phone ; 
 int age ; 
 User( this . firstName , this . lastName ); 
 } 
 // Usage 
 var user = new User( 'John' , 'Doe' ) 
 .. age = 30 
 .. phone = '+123456789' ; 35

Automatic Fluent APIs querySelector( 'h1' ) 
 ..text = 'Welcome!' 
 ..classes.add( 'caption' ) 
 ..onClick.listen((_) => print( 'clicked' )); 36