我试图创建一个属性的获取和设置方法:
private _name: string;
Name() {
get:
{
return this._name;
}
set:
{
this._name = ???;
}
}
设置值的关键字是什么?
我试图创建一个属性的获取和设置方法:
private _name: string;
Name() {
get:
{
return this._name;
}
set:
{
this._name = ???;
}
}
设置值的关键字是什么?
当前回答
TS提供了getter和setter,使对象属性能够更好地控制如何在对象外部访问(getter)或更新(setter)。不是直接访问或更新属性,而是调用代理函数。
例子:
class Person {
constructor(name: string) {
this._name = name;
}
private _name: string;
get name() {
return this._name;
}
// first checks the length of the name and then updates the name.
set name(name: string) {
if (name.length > 10) {
throw new Error("Name has a max length of 10");
}
this._name = name;
}
doStuff () {
this._name = 'foofooooooofoooo';
}
}
const person = new Person('Willem');
// doesn't throw error, setter function not called within the object method when this._name is changed
person.doStuff();
// throws error because setter is called and name is longer than 10 characters
person.name = 'barbarbarbarbarbar';
其他回答
下面是一个工作示例,可以为你指明正确的方向:
class Foo {
_name;
get Name() {
return this._name;
}
set Name(val) {
this._name = val;
}
}
JavaScript中的getter和setter只是普通的函数。setter是一个接受参数的函数,该参数的值就是被设置的值。
你可以这样写
class Human {
private firstName : string;
private lastName : string;
constructor (
public FirstName?:string,
public LastName?:string) {
}
get FirstName() : string {
console.log("Get FirstName : ", this.firstName);
return this.firstName;
}
set FirstName(value : string) {
console.log("Set FirstName : ", value);
this.firstName = value;
}
get LastName() : string {
console.log("Get LastName : ", this.lastName);
return this.lastName;
}
set LastName(value : string) {
console.log("Set LastName : ", value);
this.lastName = value;
}
}
如果你正在使用TypeScript模块,并试图添加一个导出的getter,你可以这样做:
// dataStore.ts
export const myData: string = undefined; // just for typing support
let _myData: string; // for memoizing the getter results
Object.defineProperty(this, "myData", {
get: (): string => {
if (_myData === undefined) {
_myData = "my data"; // pretend this took a long time
}
return _myData;
},
});
然后,在另一个文件中:
import * as dataStore from "./dataStore"
console.log(dataStore.myData); // "my data"
TS提供了getter和setter,使对象属性能够更好地控制如何在对象外部访问(getter)或更新(setter)。不是直接访问或更新属性,而是调用代理函数。
例子:
class Person {
constructor(name: string) {
this._name = name;
}
private _name: string;
get name() {
return this._name;
}
// first checks the length of the name and then updates the name.
set name(name: string) {
if (name.length > 10) {
throw new Error("Name has a max length of 10");
}
this._name = name;
}
doStuff () {
this._name = 'foofooooooofoooo';
}
}
const person = new Person('Willem');
// doesn't throw error, setter function not called within the object method when this._name is changed
person.doStuff();
// throws error because setter is called and name is longer than 10 characters
person.name = 'barbarbarbarbarbar';
下面是如何添加getter和setter的示例
class Person {
private _age: number;
private _firstName: string;
private _lastName: string;
public get age() {
return this._age;
}
public set age(theAge: number) {
if (theAge <= 0 || theAge >= 200) {
throw new Error('The age is invalid');
}
this._age = theAge;
}
public getFullName(): string {
return `${this._firstName} ${this._lastName}`;
}
}