Dart language - the basis of content

basis

• The main function

  void main ( ) { }

• Declare variables

  • var a num a int a double a bool a = true
  • final b = 0; declaration of variables can only be assigned once
  • const a = 1; Constant
  • var a = const [1,2]; declare a list of immutable

type of data

• type of data

  • Number
    • Int - integer
    • double - float
  • String
  • Boolean
  • List - Array
  • Map - value pairs

• Special operators ~ / rounding down

• String Manipulation

  • ''' hello dddd''' It represents multi-line strings, reserved wrap

  • 'hello \n Dart' 会换行

  • String aa = r''hello \n Dart" I will not wrap. Will output \ n

  • 'abc' * 2 == 'abcabc'

  • 'abc'[1] == 'b'

  • Interpolation string " a + b = ${a + b}" ${xx}is an expression only one variable $ a written interpolation may be omitted

• Map key-value pairs

  • create var qq = {'first' : 'Dart' , 'second' : 'java'};
  • Create an immutable Map var q = const { ,,,, }
  • Construction create var q = new Map()
  • Acquisition value qq['frist']
  • Cycle pass two values qq.forEach ( f ); void f( key , value ){.......}
• dynamic type - dynamic type
  • var a = 10; a = "xxx";
  • dynamic a = 20; a="xxx";
  • Generic Application: var lis = new List\<dynamic\>();LIS Such statements may use various types of data

Operators

• = ?? b ??= 10;B 10 is empty, there is no change value.
• a~/=b Similar to a + = b
  
• var c = a ?? b empty expression is a value of b

function

• void main () {} void return type is a position as not needing void return type
• Dart defined function xxx(){}js function is definedfunction xx () {}
• void fun(String name , int age) {xxxx}
• Optional parameters wording
  • fun(String name , {int age, String kk}) fun('张三',age:20) Position is not fixed
  • fun(String name , [int age , String kk]) fun('张三' , 20 ) Fixed position
• Parameter Default
  • fun(String name , {int age = 30, String kk})
• Anonymous Methods
  • () {} Can be assigned to variables or called directly .. it can not be defined directly in the outermost
  • ((){})() Self-adjusting since the implementation of

Object-Oriented

class class-

• Create a new class declaration class objects .new be omitted by default all objects inherit from the Object class

• class property defaults have getter and setter methods require custom --java

• Property class final statement is read-only

• class methods can not be overloaded

• //举例
  class Person {
    String name;
    int age;
    void work(){
        print("name is $name , age is $age")
    },
      Person (String name , int age){//构造方法
          this.name = name;
          this.age = age;
      };
      Person (this.name,this.age);//构造方法简写
      Person.ddd (){}; //带名称的构造方法
  }
  //调用
  var person = new Person();//new Person('Tom'.20)--有构造时
  person.name = 'Tom';
  person.age = 20;
  person.work();  //name is Tom , age is 20

• Use _represented privacy default a file is a library .. Dart Dart set the visibility of visibility to Library (library) is very much a unit of java

• class calculated property

  • class Rect{
        num width,height;
        num get area => width * height;// area{ return w*h }
        set area(val) {//给计算属性area赋值时,处理数据,给其他属性赋值
            width = val / 20;
        };
    }
    var re = new Rect();
    re.height = 20;
    re.width = 10;
    print(re.area); //200

• Construction method - a method called when creating an object can set up multiple configurations fancy details above person ..

  • Named Constructor
  • ---- If constant constructor class is immutable state, it is a compile-time constants corresponding to the object
    • 使用const声明构造方法,并且所有变量都为final,使用const声明对象.可以省略
  • Factory construction method
    • Factory design pattern similar to the pattern - - plus factory before constructor
    • The biggest difference, plant construction, can return objects. --- ???
  • Initialization list --- ???
• static declares a static member - ???
• Object operator
  • ?.安全访问成员 person?.work() 对象存在时调用work不存在则不执行
  • as 类型转换
  • is is! 是否是指定类型
  • 级联操作 person..name='xx'..age=20..work();
• Object method call
  • If the class implements call (), the object class can be used as a method

inherit

• extends -. Visible inherit the parent class attributes and methods subclass can rewrite the parent class method / getter / setter
• Single inheritance / polymorphism
• @override - means that the method is reproducible
• Subclass constructor default constructor calls the parent class unnamed Senate. If the parent does not need to display the call
• Constructor execution sequence: initialization list subclass - parent class constructor - construction of subclasses

Abstract class

• Abstract class abstract, can not be instantiated. It can only be inherited instantiated

interface

• Classes and interfaces are unified