Sprachkonzepte

Übersicht: Sprachkonzepte

• Objektorientiert
• Optionale Typen
• Build-in Typen
• Closures
• Klassen
• Mixins
• Vererbung
• Nebenläufigkeit mit Isolates
• Die DOM
• Code Beispiele
• Der Vergleich

Objektorientiert

int nummer = 42.7.round(); // 43

List str = "Dart;JS;C++;Java".split(";");

var IntOrStr = 3 + "4";

Klassen

Beispiel

class Apple
{
  String type;
  String color;
  Apple (this.type);
  
  getInfo () {
    return '$color $type'
           ' apple';
  }
}

var apple = new Apple('Mac');
apple.color = 'green';
window.alert(apple.getInfo()); // "green Mac apple"

class Apple {
  String _type;
  String _color;
  Apple (this.type);
  
  _getInfo() => '$color $type' ' apple';
}

JavaScript Version von der Apple-klasse

function Apple (type) {
	this.type = type;
	this.color = "red";
}

Apple.prototype.getInfo = function() {
return this.color + ' ' +
this.type + ' apple';
};

var apple = new Apple('Mac');
apple.color = 'reddish';
alert( apple.getInfo() );

Vererbung

 1  abstract class Shape {
 2    num perimeter();
 3  }
 4
 5  class Rectangle implements Shape {
 6    num height, width; 
 7    Rectangle(this.height, this.width);
 8    num perimeter() => 2*height + 2*width;
 9  }
10
11  class Square extends Rectangle {
12    Square(num size) : super(size, size);
13  }

Optionale Typen

Ein einfache Beispiel:

 1  class Person {}
 2
 3  class Customer extends Person
 4  {
 5     buy() { print("bought"); }
 6  }
 7
 8  main() {
 9     Person p = new Customer();
10     p.buy();
11  }

 1  class Point {
 2      var x, y;
 3      Point(this.x, this.y);
 4  
 5      distanceTo(other) {
 6        var dx = x - other.x;
 7        var dy = y - other.y;
 8        return sqrt(dx * dx + dy * dy);
 9      }
10  }
11
12  main() {
13      var p = new Point(2, 3);
14      var q = new Point(3, 4);
15      print('distance from p to'
16            ' q = ${p.distanceTo(q)}');
17  }

 1  class Point {
 2      num x, y;
 3      Point(this.x, this.y);
 4  
 5      num distanceTo(Point other) {
 6        num dx = x - other.x;
 7        num dy = y - other.y;
 8        return sqrt(dx * dx + dy * dy);
 9      }
10  }
11
12  main() {
13      Point p = new Point(2, 3);
14      Point q = new Point(3, 4);
15      print('distance from p to'
16            ' q = ${p.distanceTo(q)}');
17  }

 1  class Point {
 2      var x, y;
 3      Point(this.x, this.y);
 4  
 5      void distanceTo(String other) {
 6        var dx = x - other.x;
 7        String dy = y - other.y;
 8        return sqrt(dx * dx + dy * dy);
 9      }
10  }
11
12  main() {
13      var p = new Point(2, 3);
14      String q = new Point(3, 4);
15      print('distance from p to'
16            ' q = ${p.distanceTo(q)}');
17  }

Build-in Typen

var bigInt = 346538465234590347592847298346243459756895347698465298346583746592374652378462347569234765834765947569827346583465243765923847659234765928347659567398475647495873984572947593470294387093493456870849216348723763945678236420938467345762304958724596873045876234572037862934765294365243652548673456705673465273465246734506873456729457623845623456234650457693475603768922346728346256;
print(bigInt); // In Dart VM -> OK / in JS -> Infinity

if (1) {
	// In Javascript -> true
} else {
	// In Dart -> false
}

false, null, undefined, "", -0, 0, NaN

Closures

Beispiel:

 1  fibonacci() {
 2    int x = 0;
 3    int y = 1;
 4    int z;
 5
 6    return () {
 7      z = x;
 8      x = y;
 9      y = z+y;
10      return y - x;
11    };
12  }
13
14  var nextfib = fibonacci();
15  print( nextfib() ); // 0
16  print( nextfib() ); // 1
17  print( nextfib() ); // 1
18  print( nextfib() ); // 2
19  print( nextfib() ); // 3
20  print( nextfib() ); // 5

Mixins

 1  class Point {
 2      var x, y;
 3
 4      distanceTo(other) {
 5  	  var dx = x - other.x;
 6  	  var dy = y - other.y;
 7  	  return sqrt(dx * dx + dy * dy);
 8  	}
 9  }

 1  class firstmixin {
 2    var number = 1;
 3    printNumOne() => print("FirstNum: $number");
 4  }
 5
 6  class secondmixin{
 7    var number = 2;
 8    printNumTwo() => print("SecondNum: $number");
 9  }
10
11  class Point extends Object with firstmixin, secondmixin {
12    printNumber() => printNumOne();
13  }
14
15  Point test = new Point();
16  test->printNumber(); // "FirstNum: 2"
16  test->printNumOne(); // "FirstNum: 2"
16  test->printNumTwo(); // "SecondNum: 2"

class AnimalLover extends Person with Dogs, Cats, Rabbits {...} 

Nebenläufigkeit mit Isolates

Die DOM

Paar Beispiele:

Code Beispiele

Die Point Klasse

Ein Popup Fenster

Einfaches DOM Manipulieren

Eine ToDo-Liste

Simple Isolates

Der Vergleich