TypeScript----类

一、类的属性

public: 公有，

private: 私有，不能在声明它的类的外部访问，只能在类内部访问

protect: 保护，不能在声明它的类的外部访问，但继承者除外

readonly 只读属性，必须在声明时或构造函数里被初始化

static静态属性，无需实例化就可以访问静态成员

super()方法，它会执行基类的构造方法

class Grid {
    static origin = {x: , y: };
    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: , y: }));
console.log(grid2.calculateDistanceFromOrigin({x: , y: }));

二、类的存取，set() 和 get()

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!");
        }
    }
}

let employee = new Employee();
employee.fullName = "Bob Smith";
if (employee.fullName) {
    alert(employee.fullName);
}

三、类的继承  extends

class Animal {
    name:string;
    constructor(theName: string) { this.name = theName; }
    move(distanceInMeters: number = ) {
        console.log(`${this.name} moved ${distanceInMeters}m.`);
    }
}

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

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

let sam = new Snake("Sammy the Python");
let tom: Animal = new Horse("Tommy the Palomino");

sam.move();
tom.move();

四、抽象类：abstract，派生类的基类使用。它们一般不会直接被实例化。

abstract class Department{
    constructor(public name:string){}
    printName():void{
        console.log('Department name:'+this.name);
    }
    abstract printMeeting():void;//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。
}
class AcountingDepartment extends  Department{
    constructor(){
        super('Accounting and Auditing');
    }
    printMeeting():void{
        console.log('The Accounting Department meets each Monday at 10am.');
    }
    generateReports():void{
        console.log('Generating accounting reports...');
    }
}
let department:Department;
department=new Department()  //error
let department=new AcountingDepartment();
department.printName();
department.printMeeting();
//department.generateReports();