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: 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}));
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 = 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); } } class Horse extends Animal { constructor(name: string) { super(name); } move(distanceInMeters = 45) { 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(34);
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();