angular - 为什么 Angular 2+ 结构指令不更新 View ？

Question

在我的应用程序中，我有一个具有权限数组的帐户服务，所以我创建了一个结构指令来决定是否显示操作按钮，但问题是当我登录/注销并更新权限数组时，指令不会更新 View 。

代码如下:

import { Directive, Input, TemplateRef, ViewContainerRef } from '@angular/core';
import { Account } from './models';
import { AccountService } from './account.service';

@Directive({
  selector: '[appAuth]',
})
export class AuthDirective {

  @Input() set appAuth(action: string) {
    if (this._account.permissions.includes(action)) {
      this._contRef.createEmbeddedView(this._tmplRef);
    } else {
      this._contRef.clear();
    }
  }

  constructor(
    private _contRef: ViewContainerRef,
    private _tmplRef: TemplateRef<any>,
    private _account: AccountService
  ) { }

}

这是指令用法的示例:

<button
  class="btn btn-default"
  *appAuth="'find-accounts'"
  (click)="doSomething()">
  Find Accounts
</button>

Answer 1

import { Account, AccountService } from '../common';
import { Subscription } from 'rxjs/Subscription';
import {
  Directive, Input, TemplateRef, ViewContainerRef, OnInit, OnDestroy
} from '@angular/core';

@Directive({
  selector: '[appAuth]',
})
export class AuthDirective implements OnInit, OnDestroy {

  private _accountChangesSubscription: Subscription;

  @Input('appAuth') private appAuth: string;

  constructor(
    private _contRef: ViewContainerRef,
    private _tmplRef: TemplateRef<any>,
    private _account: AccountService
  ) { }

  ngOnInit() {
    this._accountChangesSubscription = this._account.changes$
      .subscribe((account: Account) => {
        const permissions = this._account.permissions;

        if (permissions && permissions.includes(this.appAuth)) {
          this._contRef.createEmbeddedView(this._tmplRef);
        } else {
          this._contRef.clear();
        }
      });
  }

  ngOnDestroy() {
    this._accountChangesSubscription.unsubscribe();
  }

}