What I m doing wrong in my Angular HTML template?

Question

I m not yet comfortable in angular when it comes to observable so I m training my self

I m writing a small app where I manage boxing club

I want to show last 3 attended lesson of the current selected boxer

So I tried the following

 <div class="col-6">
        <div *ngIf="lessons">
            <div *ngIf="(lessons|async).length > 0">
                <h2>les 3 derniere lessons </h2>
                <hr>
                <ul class="list-group" style="user-select: auto;">
                    <li *ngFor=" let lesson in (lessons | async) | slice:0:3; let i=index "
                        class="list-group-item d-flex justify-content-between align-items-center"
                        style="user-select: auto;">
                        <a [routerLink]="['/lesson', lesson.id, 'view' ]">
                            <span class="badge badge-primary badge-pill" style="user-select: auto;">{{i}}</span>
                            {{lesson.detail}}
                        </a>

                    </li>
                </ul>
            </div>

        </div>
        <div *ngIf="versements">
            <div *ngIf="(versements|async).length > 0">
                <h2>les 3 derniere versements </h2>
                <hr>
                <ul class="list-group" style="user-select: auto;">
                    <li *ngFor=" let versement in (versements | async ) | slice:0:3; let i=index "
                        class="list-group-item d-flex justify-content-between align-items-center"
                        style="user-select: auto;">
                        <a [routerLink]="['/lesson', lesson.id, 'view' ]">
                            <span class="badge badge-primary badge-pill" style="user-select: auto;">{{i}}</span>
                            {{versement.montant?}} : {{versement.date | date :'short'}}
                        </a>

                    </li>
                </ul>
            </div>
        </div>

    </div>

Where the component ts code is as below :

import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';

import { IBoxer } from 'app/shared/model/boxer.model';
import { JhiDataUtils, JhiAlertService } from 'ng-jhipster';
import { Observable, of } from 'rxjs';
import { MAN_PICTURE_PATH } from 'app/shared/constants/input.constants';
import { IVersement } from 'app/shared/model/versement.model';
import { VersementService } from '../versement/versement.service';
import { LessonService } from '../lesson/lesson.service';
import { HttpResponse, HttpErrorResponse } from '@angular/common/http';
import { ILesson } from 'app/shared/model/lesson.model';

@Component({
  selector: 'jhi-boxer-detail',
  templateUrl: './boxer-detail.component.html'
})
export class BoxerDetailComponent implements OnInit {
  boxer: IBoxer;
  versements: Observable<IVersement[]>;
  lessons : Observable<ILesson[]>;
  manPicturePath: any;

  constructor(
    protected jhiAlertService: JhiAlertService,
    protected activatedRoute: ActivatedRoute,
    protected dataUtils: JhiDataUtils,
    protected versementService: VersementService,
    protected lessonService: LessonService
  ) {

  }

  ngOnInit() {
    this.manPicturePath = MAN_PICTURE_PATH;

    this.activatedRoute.data.subscribe(({ boxer }) => {
      this.boxer = boxer;
    });


    this.versementService
      .query({ boxerID: this.boxer.id }, this.versementService.BY_BOXER_ID)
      .subscribe(
        (res: HttpResponse<IVersement[]>) => this.fetchVersementsDatas(res.body),
        (err: HttpErrorResponse) => this.JhiAlertError(err)
      );


    this.lessonService
        .query( {boxerID: this.boxer.id},this.lessonService.BY_BOXER_ID)
        .subscribe(
          (res:HttpResponse<ILesson[]>) => this.fetchLessonsDatas(res.body),
          (err:HttpErrorResponse) => this.JhiAlertError(err)
        );

  }

  fetchLessonsDatas(lessons){
    this.lessons = of(lessons);
  }

  fetchVersementsDatas(versements?: IVersement[]) {
    this.versements = of(versements);
  }

  JhiAlertError(errorMessage: any) {
    this.jhiAlertService.error(errorMessage, null, null);

  }

  byteSize(field: any) {
    return this.dataUtils.byteSize(field);
  }

  openFile(contentType: any, field: any) {
    return this.dataUtils.openFile(contentType, field);
  }

  previousState() {
    window.history.back();
  }
}

I m handling badly my template but I don't know where

Here is my console error prompt

core.js?f18e:6014 ERROR Error: Uncaught (in promise): Error: Template parse errors:
Can't bind to 'ngForIn' since it isn't a known property of 'li'. (" > 0"> <h2>les 3 derniere lessons </h2> <hr> <ul class="list-group" style="user-select: auto;"> <li [ERROR ->]*ngFor=" let lesson in (lessons | async) | slice:0:3; let i=index " class="list-group-item d-flex jus"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:1790
Property binding ngForIn not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the "@NgModule.declarations". ("ngth > 0"> <h2>les 3 derniere lessons </h2> <hr> <ul class="list-group" style="user-select: auto;"> [ERROR ->]<li *ngFor=" let lesson in (lessons | async) | slice:0:3; let i=index " class="list-group-item d-flex"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:1786
Parser Error: Unexpected end of expression:  {{versement.montant?}} : {{versement.date | date :'short'}}  at the end of the expression [ {{versement.montant?}} : {{versement.date | date :'short'}} ] in ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2622 (".id, 'view' ]"> <span class="badge badge-primary badge-pill" style="user-select: auto;">{{i}}</span>[ERROR ->] {{versement.montant?}} : {{versement.date | date :'short'}} </a> </li> </ul> </div> </div> </div> </"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2622
Parser Error: Conditional expression versement.montant? requires all 3 expressions at the end of the expression [ {{versement.montant?}} : {{versement.date | date :'short'}} ] in ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2622 (".id, 'view' ]"> <span class="badge badge-primary badge-pill" style="user-select: auto;">{{i}}</span>[ERROR ->] {{versement.montant?}} : {{versement.date | date :'short'}} </a> </li> </ul> </div> </div> </div> </"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2622
Can't bind to 'ngForIn' since it isn't a known property of 'li'. ("0"> <h2>les 3 derniere versements </h2> <hr> <ul class="list-group" style="user-select: auto;"> <li [ERROR ->]*ngFor=" let versement in (versements | async ) | slice:0:3; let i=index " class="list-group-item d-f"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2310
Property binding ngForIn not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the "@NgModule.declarations". ("h > 0"> <h2>les 3 derniere versements </h2> <hr> <ul class="list-group" style="user-select: auto;"> [ERROR ->]<li *ngFor=" let versement in (versements | async ) | slice:0:3; let i=index " class="list-group-item"): ng:///BoxingBoxerModule/BoxerDetailComponent.html@0:2306

should I now consider using **in** when I m looping on a simple array and **of** when I m looping on an observable ? — Mohammed Housseyn Taleb, Oct 26 '19 at 15:06
there is no `let item in items` in angular template. use `let item of items` always — Vishal Biswas, Oct 26 '19 at 15:09

StepUp · Accepted Answer · 2019-10-26T15:22:57.860

To iterate you need to use the following syntax *ngFor = "let value of values":

<li *ngFor="let versement of (versements | async ) | slice:0:3; let i=index">
...
</li>

As Angular docs says:

A structural directive that renders a template for each item in a collection. The directive is placed on an element, which becomes the parent of the cloned templates.

<li *ngFor="let user of userObservable | async as users; index as i; first as isFirst">
  {{i}}/{{users.length}}. {{user}} <span *ngIf="isFirst">default</span>
</li>

What I m doing wrong in my Angular HTML template?

1 Answers1