双击 Angular 指令

Question

我在 Angular 7 中有以下模板：

<ul class="posts">
  <li *ngFor="let post of posts">
    <h2>{{post.title}}</h2>
    <a (click)="delete(post)">Delete Post</a>
  </li>
</ul>

我想创建一个确认指令用作：

<a (click)="delete(post)" confirm="Confirm delete" class="delete">Delete Post</a>

点击的那一刻（一个就够了）变成：

<a (click)="delete(post)" confirm="Confirm delete" class="delete confirm">Confirm delete</a>

所以会发生什么：
- 主播的文字从“删除帖子”变为内部确认，例如“确认删除”；
- 将“确认”类添加到锚 CSS 类；
- Delete(post) 方法仅在“确认模式”上单击锚点后调用；
- 在点击“确认模式”或 5 秒后没有被点击它会回到原来的状态：

<a (click)="delete(post)" confirm="Confirm delete" class="delete">Delete Post</a>

这可以通过指令来完成吗？

import { Directive } from '@angular/core';

@Directive({
  selector: '[confirm]'
})

export class ConfirmDirective {

  constructor(el: ElementRef) {
     el.nativeElement ...
  }

}

我开始创建指令，但我真的不知道该怎么做。

Answer 1

更新：

如果你真的想要，你实际上可以使用指令来做到这一点。试试这个：

import { Directive, ElementRef, Input, Renderer2, OnInit } from '@angular/core';
import { Observable, Subject, BehaviorSubject, timer, fromEvent } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Directive({
  selector: '[confirm]'
})
export class ConfirmDirective implements OnInit {
  @Input('confirm') delete: Function;
  private confirm$ = fromEvent(this.el.nativeElement, 'click');
  private confirmTimeout: number = 5000;
  private timer$: Observable<number>;
  private isConfirming = new BehaviorSubject<boolean>(false);
  private isConfirming$ = this.isConfirming.asObservable();

  constructor(private el: ElementRef, private renderer: Renderer2) {}

  ngOnInit() {
    this.isConfirming$.subscribe((isConfirming) => this.setLabel(isConfirming));
    this.confirm$.subscribe((event: any) => this.doConfirm());
  }

  setLabel(isConfirming: boolean): void {
    // set the correct element text and styles
    let text: any;
    let textEl = this.renderer.createElement('span');

    if (this.el.nativeElement.firstChild) {
      this.renderer.removeChild(this.el.nativeElement, this.el.nativeElement.firstChild);
    }
    if (this.isConfirming.value) { // we are confirming right now
      text = this.renderer.createText('Please confirm delete');
      this.renderer.addClass(this.el.nativeElement, 'delete');
    } else {
      text = this.renderer.createText('Delete');
      this.renderer.removeClass(this.el.nativeElement, 'delete');
    }

    this.renderer.appendChild(this.el.nativeElement, text);
  }

  doConfirm(): void {
    if (this.isConfirming.value === false) { // start confirming
      this.timer$ = timer(this.confirmTimeout);
      this.isConfirming.next(true);

      // start the timer
      this.timer$
          .pipe(
            takeUntil(this.confirm$) // stop timer when confirm$ emits (this happens when the button is clicked again)
          )
            .subscribe(() => {
            this.isConfirming.next(false); // timeout done - confirm cancelled
        });
    } else { // delete confirmation
      this.isConfirming.next(false);
      this.delete(); // this is the delete action that was passed to the directive
    }
  }
}

您可以将它应用于这样的元素，将实际的delete 方法作为参数传递。

<button type="button" [confirm]="delete"></button>

工作示例：https://stackblitz.com/edit/angular-wdfcux

旧答案：

不确定指令是否是最好的方法。它可能会完成，但您必须以某种方式拦截点击处理程序和/或将删除方法传递给它。可能会很乱。

我可能会为删除按钮创建一个组件并在那里处理它（实际上这是一个谎言，如果这是我，我会使用原生的confirm 对话框并完成它，但你不想要）。

类似这样的：

import { Component } from '@angular/core';
import { Observable, Subject, timer } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Component({
  selector: 'delete-button',
  template: `<button type="button" (click)="delete()" [ngClass]="{ delete: isConfirming }">{{ label }}</button>`,
  styles: ['.delete { background-color: teal; color: white; } ']
})
export class DeleteButtonComponent {
  private confirmTimeout: number = 5000;
  private timer$: Observable<number>;
  private cancelTimer = new Subject();
  public isConfirming: boolean = false;

  constructor() {}

  get label(): string {
    return this.isConfirming
      ? 'Please confirm delete'
      : 'Delete'
  }

  delete() {
    if (!this.isConfirming) {
      this.timer$ = timer(this.confirmTimeout);
      this.isConfirming = true;

      this.timer$
          .pipe(
            takeUntil(this.cancelTimer)
          ).subscribe(() => {
            this.isConfirming = false;
        }, null, () => this.isConfirming = false);
    } else {
      this.cancelTimer.next();
      // really delete
    }
  }
}

工作示例：https://stackblitz.com/edit/angular-z6fek4

Answer 2

你可以使用 rxjs takeUntil，

posts: any[] = [
  { id: 1, title: 'post 1', deleteText: 'Delete Post' },
  { id: 2, title: 'post 2', deleteText: 'Delete Post' }
];

delete(post) {
  post.deleteText = 'Click to Confirm';
  post.css = 'custom';
  let confirm$ = fromEvent(document.getElementById('post-' + post.id), 'click');
  let timer$ = timer(5000)

  confirm$
    .pipe(
      takeUntil(timer$)
    )
    .subscribe(() => {
      console.log('ready to delete');
      this.posts = this.posts.filter(p => p.id !== post.id);
    });



  timer$
    .subscribe(() => {
      if (this.posts.find(p => p.id === post.id)) {
        console.log('timer is up, abort delete');
        post.deleteText = 'Delete Post';
        post.css = '';
      }
    });
  }

HTML：

<ul class="posts">
   <li *ngFor="let post of posts">
      <h2>{{post.title}}</h2>
      <a (click)="delete(post)" [ngClass]="post.css" [id]="'post-'+post.id">          {{post.deleteText}}</a>
  </li>
</ul>

演示：https://stackblitz.com/edit/angular-7-master-xg8phb

（也需要管理订阅）

Answer 3

您可以通过带有@HostBinding 和@HostListener 的指令以及绑定到指令本身的任意@Inputs 来添加宿主元素行为绑定和侦听器：

@Directive({
  selector: '[confirm]'
})

export class ConfirmDirective {

  @HostListener('dblclick') onDoubleClick(event) {
    // .. do double click logic, just like binding (dbclick) to an element
  }

  @HostBinding('class.confirm') confirmStyle: boolean; // toggles class on host, just like with template binding

  @Input('confirm') confirm: boolean; // State from outside the directive that can be bound to the directive attribute directly, i.e. 'click to confirm' box

  constructor(el: ElementRef) {
     el.nativeElement ...
  }

}

如果您希望直接为确认按钮添加带有指令的 HTML / 标记，则此行为最好用组件包装。组件用于视图；指令是针对行为的。一个想法是将确认对话框（？）包装到指令可以调用的服务中。