双击 Angular 指令

Question

I have the following template in Angular 7:

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

I would like to create a confirm directive to be used as:

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

The moment is clicked (one is enough) it changes to:

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

So what happens is:
- Anchor's text changes from "Delete Post" to the one inside confirm, eg "Confirm Delete";
- Class "confirm" is added to anchor CSS classes;
- Delete(post) method is only called after anchor being clicked on "confirm mode";
- After being clicked on "confirm mode" OR 5 seconds go by without being clicked it goes to its original state:

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

Can this be done with a directive?

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

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

export class ConfirmDirective {

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

}

I started to create the directive but I am really not sure how to do this.

Answer 1

Update:

If you really want to, you actually can do it with a directive. Try this:

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
    }
  }
}

You would apply it to an element like this, passing in the actual delete method as a parameter.

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

Working example: https://stackblitz.com/edit/angular-wdfcux

Old answer:

Not sure a directive would be the best way to go. It could probably be done but you'd have to intercept the click handler somehow and/or pass the delete method to it. It would probably be messy.

I'd probably create a component for the delete button and handle it there (well actually that's a lie, if this were me I'd use the native confirm dialog and be done with it, but you don't want to).

Something like this:

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
    }
  }
}

Working example: https://stackblitz.com/edit/angular-z6fek4

Answer 2

You can use 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>

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

(also need to manage subscriptions)

Answer 3

You can add host element behavior bindings and listeners through a directive with @HostBinding and @HostListener , as well as arbitrary @Input s bound to the directive itself:

@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 ...
  }

}

If you're looking to directly add HTML / markup with the directive for a confirm button, this behavior is instead better wrapped with a component instead. Components are for views; directives are for behavior. One idea is to wrap the confirm dialog(?) into a service that the directive can call.