2.类.ts

1.类：
class Greeter {
    greeting: string;
    constructor(message: string) {
        this.greeting = message;
    }
    greet() {
        return "Hello, " + this.greeting;
    }
}

2.继承：包含构造函数的派生类必须调用 super()，它会执行基类的构造方法
class Animal {
    name:string;
    constructor(theName: string) { this.name = theName; }
    move(distanceInMeters: number = 0) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

class Snake extends Animal {
    constructor(name: string) { super(name); }
    move(distanceInMeters = 5) {
        console.log("Slithering...");
        super.move(distanceInMeters);
    }
}

3.访问修饰符：公共，私有与受保护的修饰符
1).默认为public
class Animal {
    public name: string;
    public constructor(theName: string) { this.name = theName; }
    public move(distanceInMeters: number) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

2).private 当成员被标记成private时，它就不能在声明它的类的外部访问
class Animal {
    private name: string;
    constructor(theName: string) { this.name = theName; }
}

3).protected protected成员在派生类中仍然可以访问
class Person {
    protected name: string;
    protected constructor(theName: string) { this.name = theName; }
}

// Employee can extend Person
class Employee extends Person {
    private department: string;

    constructor(name: string, department: string) {
        super(name);
        this.department = department;
    }

    public getElevatorPitch() {
        return `Hello, my name is ${this.name} and I work in ${this.department}.`;
    }
}

4).readonly修饰符 只读属性必须在声明时或构造函数里被初始化
class Octopus {
    readonly name: string;
    readonly numberOfLegs: number = 8;
    constructor (theName: string) {
        this.name = theName;
    }
}
let dad = new Octopus("Man with the 8 strong legs");
dad.name = "Man with the 3-piece suit"; // error! name is readonly.

5).参数属性 参数属性通过给构造函数参数添加一个访问限定符来声明
class Animal {
    constructor(private name: string) { }
    move(distanceInMeters: number) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

4.存取器 getters/setters来截取对对象成员的访问
let passcode = "secret passcode";

class Employee {
    private _fullName: string;

    get fullName(): string {
        return this._fullName;
    }

    set fullName(newName: string) {
        if (passcode && passcode == "secret passcode") {
            this._fullName = newName;
        }
        else {
            console.log("Error: Unauthorized update of employee!");
        }
    }
}

5.静态属性 static
class Grid {
    static origin = {x: 0, y: 0};
    calculateDistanceFromOrigin(point: {x: number; y: number;}) {
        let xDist = (point.x - Grid.origin.x);
        let yDist = (point.y - Grid.origin.y);
        return Math.sqrt(xDist * xDist + yDist * yDist) / this.scale;
    }
    constructor (public scale: number) { }
}

let grid1 = new Grid(1.0);  // 1x scale
let grid2 = new Grid(5.0);  // 5x scale

console.log(grid1.calculateDistanceFromOrigin({x: 10, y: 10}));
console.log(grid2.calculateDistanceFromOrigin({x: 10, y: 10}));

6.抽象类 abstract 抽象方法必须包含 abstract关键字并且可以包含访问修饰符
抽象类做为其它派生类的基类使用
不同于接口，抽象类可以包含成员的实现细节
一般不会直接被实例化
抽象方法的语法与接口方法相似，两者都是定义方法签名但不包含方法体
abstract class Animal {
    abstract makeSound(): void;
    move(): void {
        console.log('roaming the earch...');
    }
}

1).抽象类中的抽象方法不包含具体实现并且必须在派生类中实现
abstract class Department {

    constructor(public name: string) {}

    printName(): void {
        console.log('Department name: ' + this.name);
    }

    abstract printMeeting(): void; // 必须在派生类中实现
}

class AccountingDepartment extends Department {

    constructor() {
        super('Accounting and Auditing'); // constructors in derived classes must call super()
    }

    printMeeting(): void {
        console.log('The Accounting Department meets each Monday at 10am.');
    }

    generateReports(): void {
        console.log('Generating accounting reports...');
    }
}

7.高级技巧
1).构造函数 构造函数也包含了类的所有静态属性
class Greeter {
    greeting: string;
    constructor(message: string) {
        this.greeting = message;
    }
    greet() {
        return "Hello, " + this.greeting;
    }
}

let greeter: Greeter;
greeter = new Greeter("world");
console.log(greeter.greet());

let greeter;
greeter = new Greeter("world");
console.log(greeter.greet());

2.把类当做接口使用
class Point {
    x: number;
    y: number;
}

interface Point3d extends Point {
    z: number;
}

let point3d: Point3d = {x: 1, y: 2, z: 3};