angular：调用el.setAttribute导致错误

Question

我正在尝试在每个元素（标记为 el）中设置一个新属性（定义为 'data-num'），引用 [ngDN]（作为指令的实例NgDNDirective）。

概念：

下面的代码解释了 NgDNDirective 的工作原理：

TS部分：

import { Directive, Input, ElementRef, Renderer2, EventEmitter } from '@angular/core';

@Directive({
  selector: '[ngDN]'
})
export class NgDNDirective {

  private dn: number = -1

  @Input() set ngDN(dn: number) {
    this.dn = dn
  }

  @Input() set EV(ref: {ev: EventEmitter<void>}) {
    ref.ev.subscribe(() => {
      console.log('data-num:', this.dn)
      this.renderer.setAttribute(this.elRef, 'data-num', this.dn.toString())
    })
  }

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

}

@Directive({
  selector: '[ngLoop]'
})
export class NgLoopDirective {

  @Input() set ngLoop(iter_count: number) {
    this.container.clear()
    for (let i=0; i<iter_count; i++) {
      let ee: EventEmitter<void> = new EventEmitter<void>()
      let ref = {ev: ev}
      let ev = this.container.createEmbeddedView(this.template, {index: i, ev: ref})
      ev.detectChanges()
      ee.emit()
    }
  }

  constructor(private template: TemplateRef<any>,
              private container: ViewContainerRef) {}

}

HTML部分：

<ng-template [ngLoop]="10" let-i="index" let-ref="ev">
  <a href="#" [ngDN]="i" [EV]="ref"></a>
</ng-template>

问题：

经过运行测试，控制台显示如下信息：

data-num: 0

ERROR TypeError: el.setAttribute is not a function Stack trace: ../../../platform-browser/@angular/platform-browser.es5.js/DefaultDomRenderer2.prototype.setAttribute@http://localhost:8888/vendor.bundle.js:78803:13 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:66266:9 set/<@http://localhost:8888/main.bundle.js:869:17 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:56260:36 ../../../../rxjs/Subscriber.js/SafeSubscriber.prototype.__tryOrUnsub@http://localhost:8888/vendor.bundle.js:1558:13 ../../../../rxjs/Subscriber.js/SafeSubscriber.prototype.next@http://localhost:8888/vendor.bundle.js:1505:17 ../../../../rxjs/Subscriber.js/Subscriber.prototype._next@http://localhost:8888/vendor.bundle.js:1445:9 ../../../../rxjs/Subscriber.js/Subscriber.prototype.next@http://localhost:8888/vendor.bundle.js:1409:13 ../../../../rxjs/Subject.js/Subject.prototype.next@http://localhost:8888/vendor.bundle.js:1153:17 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:56234:54 set@http://localhost:8888/main.bundle.js:928:17 updateProp@http://localhost:8888/vendor.bundle.js:63715:5 checkAndUpdateDirectiveInline@http://localhost:8888/vendor.bundle.js:63407:19 checkAndUpdateNodeInline@http://localhost:8888/vendor.bundle.js:64945:17 checkAndUpdateNode@http://localhost:8888/vendor.bundle.js:64884:16 debugCheckAndUpdateNode@http://localhost:8888/vendor.bundle.js:65745:38 debugCheckDirectivesFn@http://localhost:8888/vendor.bundle.js:65686:13 View_HomeComponent_4/<@ng:///AppModule/HomeComponent.ngfactory.js:121:9 debugUpdateDirectives@http://localhost:8888/vendor.bundle.js:65671:12 checkAndUpdateView@http://localhost:8888/vendor.bundle.js:64851:5 callViewAction@http://localhost:8888/vendor.bundle.js:65216:21 execEmbeddedViewsAction@http://localhost:8888/vendor.bundle.js:65174:17 checkAndUpdateView@http://localhost:8888/vendor.bundle.js:64852:5 callViewAction@http://localhost:8888/vendor.bundle.js:65216:21 execComponentViewsAction@http://localhost:8888/vendor.bundle.js:65148:13 checkAndUpdateView@http://localhost:8888/vendor.bundle.js:64857:5 callViewAction@http://localhost:8888/vendor.bundle.js:65216:21 execEmbeddedViewsAction@http://localhost:8888/vendor.bundle.js:65174:17 checkAndUpdateView@http://localhost:8888/vendor.bundle.js:64852:5 callViewAction@http://localhost:8888/vendor.bundle.js:65216:21 execComponentViewsAction@http://localhost:8888/vendor.bundle.js:65148:13 checkAndUpdateView@http://localhost:8888/vendor.bundle.js:64857:5 callWithDebugContext@http://localhost:8888/vendor.bundle.js:66071:39 debugCheckAndUpdateView@http://localhost:8888/vendor.bundle.js:65611:12 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:62782:9 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:57420:58 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:57420:13 next/<@http://localhost:8888/vendor.bundle.js:57297:100 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:2936:17 onInvoke@http://localhost:8888/vendor.bundle.js:56503:24 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:2935:17 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:2686:24 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:56434:54 next@http://localhost:8888/vendor.bundle.js:57297:70 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:56248:36 ../../../../rxjs/Subscriber.js/SafeSubscriber.prototype.__tryOrUnsub@http://localhost:8888/vendor.bundle.js:1558:13 ../../../../rxjs/Subscriber.js/SafeSubscriber.prototype.next@http://localhost:8888/vendor.bundle.js:1505:17 ../../../../rxjs/Subscriber.js/Subscriber.prototype._next@http://localhost:8888/vendor.bundle.js:1445:9 ../../../../rxjs/Subscriber.js/Subscriber.prototype.next@http://localhost:8888/vendor.bundle.js:1409:13 ../../../../rxjs/Subject.js/Subject.prototype.next@http://localhost:8888/vendor.bundle.js:1153:17 ../../../core/@angular/core.es5.js/http://localhost:8888/vendor.bundle.js:56234:54 checkStable@http://localhost:8888/vendor.bundle.js:56468:13 onLeave@http://localhost:8888/vendor.bundle.js:56547:5 onInvokeTask@http://localhost:8888/vendor.bundle.js:56497:17 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:2968:17 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:2736:28 ../../../../zone.js/dist/zone.js/http://localhost:8888/polyfills.bundle.js:3043:24 invokeTask@http://localhost:8888/polyfills.bundle.js:3915:9 globalZoneAwareCallback@http://localhost:8888/polyfills.bundle.js:3933:17

这意味着从NgLoopDirective到NgDNDirective注入的Renderer2实例没有setAttribute方法。为什么会出现这种情况？

angular：调用el.setAttribute导致错误

angular: Calling el.setAttribute results in an error

javascript

renderer

setattribute

typescript

angular

概念：

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