小编Tar*_*n..的帖子

我的 HTML 代码：

 <div class="dropdown-menu dropdown-menu-right filter-dropdown-menu  row">
     <input type="radio" class="filter-dropdown-menu-padding" (click)="filter_source_type(0)" name="gender" value="male"> Admin
     <input type="radio" class="filter-dropdown-menu-padding" (click)="filter_source_type(1)" name="gender" value="male"> Manager
     <input type="radio" class="filter-dropdown-menu-padding" (click)="filter_source_type(2)" name="gender" value="male"> Member<br>

 </div>

重置 HTML 代码：

<div class="btn btn-primary btn-reset" (click)="reset_filter()">Reset</div>

我的 ts 重置代码：

reset_filter() {
this.filter_source_type_value =null;
}

<div id="search-component">
    <h4>Hero Search</h4>

    <input #search Box id="searchbox"  
    ( keyup )="search( searchBox.value)" />

    <ul class="search-result">
        <li *ng For="let hero of heroes$ | a sync" >
            <a router Link="/detail/{{hero.id}}">
                {{hero.name}}
            </a>
        </li>
    </ul>
</div>

• 这段代码中$的含义是什么？
• $ 和 ngFor 标签有什么用？

import { Injectable } from '@angular/core';
import { CanActivate } from '@angular/router';
import { AuthService } from './auth.service';

@Injectable()
export class CanActivateViaAuthGuard implements CanActivate {

  constructor(private authService: AuthService) {}

  canActivate() {
    return this.authService.isLoggedIn();
  }
} 

canActivate和canDeactivate属性是什么意思？