TypeScript学习笔记之类

class Person {
    x: number;      // 默认为public类型
    y: number;
    constructor(x1: number, y1: number) {       // 默认为public类型
        this.x = x1;
        this.y = y1;
    }
}

let test = new Person(12, 34)

class Person {
    constructor(public x1: number, public y1: number) {}    // 注意这里的实现
}

let test = new Person(12, 34)

class Person {
    constructor(public x1: number, public y1: number) { }
    greet() {
        return this.x1 + '-' + this.y1;
    }
}

class A extends Person {
    constructor(x: number, y: number) {
        super(x, y);
        // ...
    }
    greet2() {
        return this.greet()
    }
}

let test = new A(12, 23);
console.log('extends from Person: ', test.greet());   // extends from Person:  12-23
console.log('self method: ', test.greet2());        // self method:  12-23

注意：
    派生类包含了一个构造函数，它必须调用 super()，它会执行基类的构造函数。而且，在构造函数里访问 this的属性之前，我们一定要调用 super()。 这个是TypeScript强制执行的一条重要规则。
    当然，调用super之后在A类中你可以像Person类中那样进行后续处理。

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

let animal = new Animal('rabbit 兔子');
animal.move(1);        // rabbit 兔子 moved 1m.
animal.name = '狗熊，忘了英文咋写了';
animal.move(200);       // 狗熊，忘了英文咋写了 moved 200m.

class Animal {
    private name: string;
    constructor(theName: string) { this.name = theName; }
}

class Rhino extends Animal {
    constructor(public age: number) { super("Rhino"); }
}

let test = new Animal('狗娃');
// test.name       // wrong！访问不到，因为name私有

let test2 = new Rhino(23);
test2.age       // 23

class Person {
    protected name: string;
    protected constructor(theName: string) { this.name = theName; }
}

// Employee 能够继承 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}.`;
    }
}

let howard = new Employee("Howard", "Sales");
// let john = new Person("John"); // 错误: 'Person' 的构造函数是被保护的.可以被继承，不能直接new

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"; // 错误! name 是只读的.

class Person {
    private _name: string;
    set name(theName: string) {
        console.log('-----------')
        this._name = theName;
    }
    get name(): string {
        return this._name + '********';
    }
}

let test = new Person();
test.name = 'admin'
console.log(test.name)

-----------
admin********

注意：
    get存取器必须要有返回值，没有返回值可以写void返回，返回不确定可以使用any类型。

class Grid {
    static origin = { x: 0, y: 0 };
    static test;
    constructor (public scale: number) { }
    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;
    }
    testValue() {
        console.log('testing: ', Grid.test);
    }
}

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

console.log(grid1.calculateDistanceFromOrigin({x: 10, y: 10}));     // 14.142135623730951
console.log(grid2.calculateDistanceFromOrigin({ x: 10, y: 10 }));    // 2.8284271247461903
console.log(grid1.testValue());    // testing:  undefined

注意：
    static字段调用的时候直接使用：类名.字段名 调用，实例字段使用：(new Class).字段名 调用，当然class内部直接使用this调用。

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'); // 在派生类的构造函数中必须调用 super()
    }

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

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

let department: Department; // 允许创建一个对抽象类型的引用
// department = new Department(); // 错误: 不能创建一个抽象类的实例
department = new AccountingDepartment(); // 允许对一个抽象子类进行实例化和赋值
department.printName();
department.printMeeting();
// department.generateReports(); // 错误: 方法在声明的抽象类中不存在

let accountingDepartment: AccountingDepartment;
accountingDepartment = new AccountingDepartment();
accountingDepartment.generateReports();

注意：
    1、abstract的class不能直接被new，只能被extends
    2、abstract的method必须被子类实现