使用 switchmap 和 forkjoin 链接 observables 不能按预期工作

Question

im currently creating trying to create a system where if i successfully updated a request i trigger 3 observables in a forkjoin then once those are finished console.log('complete/or finish') otherwise if it is not do nothin. currently though the observables are completing before the forkjoin is complete and im completely at a loss of what's happening,

 copyAttachments(): Observable<any> { if (this.model.attachments.length > 0) { return this.attachmentService.copyAttachments(this.model.attachments, this.model.id); } return empty(); } uploadAttachments(): Observable<any> { this.showAttachmentsUploadingModal = true; const formData = new FormData(); if (this.formAttachments.length > 0) { this.showAttachmentsUploadingModal = true; this.formAttachments.forEach(file => { formData.append('files', file, file.name); }); } // uploading empty formData will still trigger creation of default folder structure return this.attachmentService.uploadAttachments(formData, this.model.id); } uploadCustomerData(): Observable<any> { this.showAttachmentsUploadingModal = true; const formData = new FormData(); if (this.formCustomerData.length > 0) { this.showAttachmentsUploadingModal = true; this.formCustomerData.forEach(file => { formData.append('files', file, file.name); }); return this.attachmentService.uploadCustomerData(formData, this.model.id); } return empty(); }

 handleAttachments(): Observable<any> { return forkJoin ( this.copyAttachments(), this.uploadCustomerData(), this.uploadAttachments() ) } updateRequest() { this.myservice.updateRequest(this.model).pipe( switchMap((saveResult: boolean) => { this.showSubmittingModal = false; if (saveResult === true) { return this.handleAttachments(); } else { return empty(); } }), ).pipe(finalize(() => { console.log('finish') })).subscribe( response => { // todo: do anything with this response from uploadAttachments()? this.showAttachmentsUploadingModal = false; }, error => { location.reload(); }, () => { console.log('complete') } ); }

the expected result is my service completes, then my forkjoin observables complete then it will console.log('finish')

currently the result is the service completes. it console.logs('finish') then my forkjoin triggers

Answer 1

The solution I found to this problem is instead of returning empty() or of() you need to return an empty object as an observable this way Forkjoin still maintains value so return of({}) and everything is fine