angular: Calling el.setAttribute results in an error

Question

I'm trying to set a new attribute (defined as 'data-num') within each element (labeled as el) referring to [ngDN] (as an instance of the directive NgDNDirective).

Concept:

The code below explains how NgDNDirective is intended to work:

1. TS part:

   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) {}
   
   }
   

2. HTML part:

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

Problem:

After running the test, the console shows me the following information:

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

This means that the injected instance of Renderer2 from NgLoopDirective to NgDNDirective, comes without setAttribute method. Why does this occur?

Further informations:

ng -v _ _ ____ _ _ / \ _ __ __ _ _ _| | __ _ _ __ / | | | | / △ \ | ' \ / _| | | | |/ _ | '| | | | | | | / \| | | | (| | || | | (| | | | || | | | // __| ||__, |__,||__,||
____|_____|| |/ @angular/cli: 1.2.3 node: 6.11.0 os: linux x64 @angular/animations: 4.3.3 @angular/common: 4.3.3 @angular/compiler: 4.3.3 @angular/core: 4.3.3 @angular/forms: 4.3.3 @angular/http: 4.3.3 @angular/platform-browser: 4.3.3 @angular/platform-browser-dynamic: 4.3.3 @angular/router: 4.3.3 @angular/cli: 1.2.3 @angular/compiler-cli: 4.3.3 @angular/language-service: 4.3.3

Answer 1

Renderer2#setAttribute(el, name, value) ends up calling el.setAttribute(name, value). What the error says is that the argument passed as el does not have a setAttribute() method. And that is because it is an ElementRef instance.

You should be passing the actual DOM element:

this.renderer.setAttribute(this.elRef.nativeElement, ...)