Question

这是一个与打字稿范围有关的问题。如果listofstuff常量在类结束括号之外，则它可以工作，但如果它在括号内

则不行

例如，此代码不起作用：

  import {Injectable} from '@angular/core'

  @Injectable()
  export class EventListService{
  getEvents(){
    return listofstuff
  }  
const listofstuff = [
  {name:'Angular Connect', date: '9/26/2036', time: '10am', location: {address: '1 London Rd', city: 'London', country: 'England'}},
  {name:'ng-nl', date: '4/15/2037', time: '9am', location: {address: '127 DT ', city: 'Amsterdam', country: 'NL'}},
  {name:'ng-conf 2037', date: '4/15/2037', time: '9am', location: {address: 'The Palatial America Hotel', city: 'Salt Lake City', country: 'USA'}},
  {name:'UN Angular Summit', date: '6/10/2037', time: '8am', location: {address: 'The UN Angular Center', city: 'New York', country: 'USA'}},
]
}

但这有效：

 import {Injectable} from '@angular/core'

  @Injectable()
  export class EventListService{
  getEvents(){
    return listofstuff
  }  
}
const listofstuff = [
  {name:'Angular Connect', date: '9/26/2036', time: '10am', location: {address: '1 London Rd', city: 'London', country: 'England'}},
  {name:'ng-nl', date: '4/15/2037', time: '9am', location: {address: '127 DT ', city: 'Amsterdam', country: 'NL'}},
  {name:'ng-conf 2037', date: '4/15/2037', time: '9am', location: {address: 'The Palatial America Hotel', city: 'Salt Lake City', country: 'USA'}},
  {name:'UN Angular Summit', date: '6/10/2037', time: '8am', location: {address: 'The UN Angular Center', city: 'New York', country: 'USA'}},
]

来自面向对象的背景（C＃和一些java），这对我来说很奇怪。谁能解释一下这里发生了什么？即使在第一个示例中使用“this”关键字也不起作用...

Answer 1

您不能将const关键字用于类属性。相反，类属性只能使用public，private，readonly和protected修饰符进行标记。

import { Injectable } from '@angular/core'

@Injectable()
export class EventListService {
  readonly listofstuff: any[] = [
    { name: 'Angular Connect', date: '9/26/2036', time: '10am', location: { address: '1 London Rd', city: 'London', country: 'England' } },
    { name: 'ng-nl', date: '4/15/2037', time: '9am', location: { address: '127 DT ', city: 'Amsterdam', country: 'NL' } },
    { name: 'ng-conf 2037', date: '4/15/2037', time: '9am', location: { address: 'The Palatial America Hotel', city: 'Salt Lake City', country: 'USA' } },
    { name: 'UN Angular Summit', date: '6/10/2037', time: '8am', location: { address: 'The UN Angular Center', city: 'New York', country: 'USA' } },
  ];

  getEvents() {
    return this.listofstuff;
  }
}

您可以使用listofstuff关键字访问this类属性。 Example

您可以在官方documentation中阅读有关Typescript类的更多信息。请记住，默认情况下，属性和没有标识符的成员会标记为public。来自文档：

在TypeScript中，默认情况下每个成员都是公开的。

希望这有帮助！

为什么const必须在typescript中的导出类之外？

1 个答案: