如何在 ngModel 值更改时使可观察对象重新发出

Question

我在我的 HTML 中使用这些可观察对象，但它们不会在我的 HTML 控件的输入值每次发生变化时重新发射（并且它们依赖于这些值，因此它们会出现的同步）。例如，当此更新 ([(ngModel)]="mappedItem.selectedBusinessEntities") 时，selectedBusinessEntitiesOptionsAsDtos$ | async 需要重新发出。看到第二个HTML控件的选项是第一个HTML控件的选中选项。我是否需要以某种方式使 [(ngModel)]="mappedItem.selectedBusinessEntities" 值成为可观察值？

HTML:

<cb-selection-list name="selectedBusinessEntities"
                   [(ngModel)]="mappedItem.selectedBusinessEntities"
                   [options]="businessEntitiesOptions$ | async"
                   [readonly]="isView()"
                   maxHeight="400px"
                   [slim]="true">
</cb-selection-list>
<cb-select label="Primary Business Entity"
           name="primaryBusinessEntity"
           [required]="true"
           [(ngModel)]="mappedItem.primaryBusinessEntity"
           [options]="selectedBusinessEntitiesOptionsAsDtos$ | async"
           [readonly]="isView()">
</cb-select>

打字稿：

@Component({
    selector: 'cb-user-details',
    templateUrl: './user-details.component.html',
    styleUrls: ['./user-details.component.scss']
})
export class UserDetailsComponent implements OnInit {

    public teamsOptions$: Observable<ITeamDto[]>;
    public userRoleTagsOptions$: Observable<ITagDto[]>;
    public userRoleTagsOptions: ITagDto[];
    public businessEntitiesOptions$: Observable<IBusinessEntityDto[]>;
    public isMobileNumberMandatory$: Observable<boolean>;
    public selectedBusinessEntitiesOptionsAsDtos$: Observable<IBusinessEntityDto[]>;

public ngOnInit(): void {
    this._initSelectOptions();
}
    
private _initSelectOptions(): void {
    this.teamsOptions$ = this.teamsLogicService.$getList();
    this.userRoleTagsOptions$ = this.tagsLogicService.$getList();
    this.businessEntitiesOptions$ = this.businessEntitiesLogicService
        .$getList()
        .pipe(
            map(businessEntities => {
                return orderBy(businessEntities, businessEntity => businessEntity?.name?.toLowerCase());
            })
        );
    this.selectedBusinessEntitiesOptionsAsDtos$ = this.businessEntitiesOptions$.pipe(
        map(businessEntities => {
            return businessEntities
                .filter(businessEntity => includes(
                    this.mappedItem.selectedBusinessEntities, businessEntity.id)
                );
        }));
    this.isMobileNumberMandatory$ = this.selectedBusinessEntitiesOptionsAsDtos$.pipe(
        map(businessEntities => {
            const buildingConsultantTag = this.userRoleTagsOptions?.find(
                tag => tag.key === USER_TAG_CONSTANTS_CONST.BUILDING_CONSULTANT);

            return this.mappedItem?.selectedTags
                .some(tag => tag === buildingConsultantTag?.id);
        })
    );
    this.isMobileNumberMandatory$.subscribe();
    this.teamsOptions$.subscribe();
    this.userRoleTagsOptions$.subscribe(res => this.userRoleTagsOptions = res);
}

编辑：

试过像这样分解 ngModel：

    <cb-selection-list name="selectedBusinessEntities"
                       [ngModel]="mappedItem.selectedBusinessEntities"
                       (ngModelChange)="selectedBusinessEntitiesChanged($event)"
                       [options]="businessEntitiesOptions$ | async"
                       [readonly]="isView()"
                       maxHeight="400px"
                       [slim]="true">
    </cb-selection-list>

学生：

public selectedBusinessEntitiesChanged(entities: number[]): void {
    this.mappedItem.selectedBusinessEntities = entities;
    this.businessEntitiesOptions$.subscribe();
    this.cdRef.detectChanges();
}

令人恼火的是，这确实导致 this.selectedBusinessEntitiesOptionsAsDtos$ 变为运行并发出新列表（使用调试器检查）。但是 UI 没有更新。这就是为什么我添加了 this.cdRef.detectChanges(); 但它不起作用的原因。

Answer 1

您可以使用 ngModelChange 事件：

(ngModelChange)="handleNgModelChangedEvent($event)

每次ngModel发生变化时都会触发。 $event 负载将保存表单字段的当前值。

更新:

另外，不确定它是否有帮助，但你不应该在私有函数中定义你的可观察对象，而是在你声明它们的地方，作为 class 成员：

例如：

businessEntitiesOptions$ = this.businessEntitiesLogicService.getList()
   .pipe(
      map(businessEntities => {
         orderBy(businessEntities, businessEntity => businessEntity?.name?.toLowerCase());
  })
);

而不是：

public businessEntitiesOptions$: Observable<IBusinessEntityDto[]>;

同样适用于所有可观察值...

您甚至应该能够在此 class.

中使用 OnPush 更改检测策略

您可以尝试在您的管道 observable 中添加 tap(x => console.log(x)) 以查看它们是否按预期工作...

例如：

.pipe(
      tap(x => console.log(x)),
      map(businessEntities => {
         orderBy(businessEntities, businessEntity => businessEntity?.name?.toLowerCase()),
      tap(x => console.log(x))
})

您可能还想删除 returns...除非您正在捕获错误或其他东西，否则您不想 return 任何东西。 Observables 只是流。

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