Class

• dart is object oriented programming with classes and mixin-based inheritance
• every oject is an instance of a class
• mixing-based inheritance means very class has exactly one super class superclass.
• class body can be reused in multiple class hierarchies
• extenstion method are used to add functionalities

using member class

• use . to refer to an instance variable or method

var p = Point(2,2);

assert(p.y == 2)

• use ? instead of . to avoid exeecption when leftmost operand is null

// If p is non-null, set a variable equal to its y value.
var a = p?.y;

constructor

• constructor names can be either class Name or ClassName.identifier

var p1 = Point(2, 2);
var p2 = Point.fromJson({'x': 1, 'y': 2})

• new is optional before constructor name

var p1 = new Point(2, 2);
var p2 = new Point.fromJson({'x': 1, 'y': 2});

• constant constructor:some class provide
• create complie time constant constructor
• write const

var p = const ImmutablePoint(2,2);

Getting an object's type

use object.runtimeType

print('The type of a is ${a.runtimeType}');

Implelemt class

class Point{
    double? x; // unitialized instance variables
    double? y; 
    double z =0; //instiallised
}

• unitiallized variables have null value
• all instance variable genereate getter method
• non final instance and late final instance variables wiithout