Angular 2 个块范围变量问题

Question

我目前正在运行一个使用 TypeScript 的 Angular 2 演示。有两个文件：作为模板导入的 index.html 文件和 TypeScript 文件。 TypeScript 文件编译成一个 pomodoro-timer.js 对于这个演示，所有类都包含在一个文件中文件：

番茄钟-timer.ts

import {
    Component,
    Input,
    Pipe,
    PipeTransform,
    Directive,
    OnInit,
    HostListener
} from '@angular/core';
import { bootstrap } from '@angular/platform-browser-dynamic';

/// Model interface 
interface Task {
    name: string;
    deadline: Date;
    queued: boolean;
    pomodorosRequired: number;
}

/// Local Data Service
class TaskService {
    public taskStore: Array<Task> = [];

constructor() {
    const tasks = [
        {
            name: "Code an HTML Table",
            deadline: "Jun 23 2015",
            pomodorosRequired: 1
        },
        {
           name: "Sketch a wireframe for the new homepage",
           deadline: "Jun 24 2016",
           pomodorosRequired: 2
        },
        {
            name: "Style table with Bootstrap styles",
            deadline: "Jun 25 2016",
            pomodorosRequired: 1
        },
        {
            name: "Reinforce SEO with custom sitemap.xml",
            deadline: "Jun 26 2016",
            pomodorosRequired: 3
        }
    ];

    this.taskStore = tasks.map(task => {
        return {
            name: task.name,
            deadline: new Date(task.deadline),
            queued: false,
            pomodorosRequired: task.pomodorosRequired
        };
    });
}

/// Component classes 

/// - Main Parent Component

@Component({
    selector: 'pomodoro-tasks',
    styleUrls: ['pomodoro-tasks.css'],
    templateUrl: 'pomodoro-tasks.html'
})

class TasksComponent {
    today: Date;
    tasks: Task[];

    constructor() {
        const TasksService: TasksService = new TasksService();
        this.tasks = taskService.taskStore;
        this.today = new Date();
    }
};

bootstrap(TasksComponent);

index.html

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Hello Angular 2!</title>
        <!-- required stylesheets -->
        <link rel="stylesheet" href="node_modules/bootstrap/dist/css/bootstrap.min.css" />
        <!-- required javascripts -->
        <script src="node_modules/es6-shim/es6-shim.min.js"></script>
        <script src="node_modules/zone.js/dist/zone.js"></script>
        <script src="node_modules/reflect-metadata/Reflect.js"></script>
        <script src="node_modules/systemjs/dist/system.js"></script>
        <script src="node_modules/rxjs/bundles/Rx.js"></script>

        <script src="systemjs.config.js"></script>
        <script>
            // importation of component module
            // with no file extension
            System.import('built/pomodoro-tasks').then(null, console.error.bind(console));
        </script>
    </head>

    <body>
        <nav class="navbar navbar-default navbar-static-top">
            <div class="container">
                <div class="navbar-header">
                    <strong class="navbar-brand">My Pomodoro Tasks</strong>
                </div>
            </div>
        </nav>
        <pomodoro-tasks></pomodoro-tasks>
    </body>
</html>

一切似乎都正常，但是，pomodoro-timer.ts 文件的这一部分似乎正在抛出一个错误：

class TasksComponent {
    today: Date;
    tasks: Task[];

    constructor() {
        // (Cannot find name 'TasksService'.at line 91 col 29, BELOW)
        // (Block-scoped variable 'TasksService' used before its declaration.at line 91 col 48, BELOW)
        const TasksService: TasksService = new TasksService();

        // (Cannot find name 'taskService'.at line 92 col 22, BELOW)
        this.tasks = taskService.taskStore;
        this.today = new Date();
    }
};

bootstrap(TasksComponent);

任何熟悉 TypeScript 的人都知道为什么我会收到这些错误吗？我正在使用带有 TypeScript 插件的 Atom IDE。

Answer 1

1) 首先你打错了 taskService 而不是 tasksService

2)您不应像在此处那样实例化 TasksService。

constructor() {
  const TasksService: TasksService = new TasksService();
  this.tasks = taskService.taskStore;
  this.today = new Date();
}

你应该把代码改成这样

constructor(private taskService:TasksService) {
  this.tasks = this.taskService.taskStore;
  this.today = new Date();
}

要了解有关依赖注入和最佳实践的更多信息，请查看此 link https://angular.io/docs/ts/latest/guide/dependency-injection.html

Answer 2

如果你像这样初始化对象

const TasksService: TasksService = new TasksService();

您将收到以下错误，

Blocked-scoped variable 'TasksService' used before its declaration.

要解决此问题，请将变量名称更改为其他名称，例如

const TaskServ: TasksService = new TasksService();

NOTE: This error usually comes when you declare a variable with the same name as of class(Object).

Angular 2 个块范围变量问题

Angular 2 Block-scoped Variable Issues

typescript

angular2-directives

angular2-decorators

angular