我在Angular HTML模板中做错了什么？

Question

关于可观察性，我还不太适应角度，所以我正在锻炼自己的自我

我正在写一个小应用来管理拳击俱乐部

我要显示当前所选拳击手的最近3堂课

所以我尝试了以下内容

 <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>

其中ts组件代码如下：

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();
  }
}

我的模板处理不好，但我不知道在哪里

这是我的控制台错误提示

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

Answer 1

要进行迭代，您需要使用以下语法*ngFor = "let value of values"：

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

As Angular docs says:
一种结构指令，可为采集。指令放置在一个元素上，该元素成为克隆模板的父级。
<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>