rxjs具有多个插入的运算符

Question

我如何在Angular 6中使用rxjs来插入项目，然后插入后我需要将不同类型的文件上传到不同的端点，新项目id作为子键，而不必嵌套所有这些调用。

createItemWithAttachments(data:any)
{    
   this.itemService.insert(data.item).subscribe((newItem:Item)=>{       
        //attachment type 1s 
        if(data.attachmentType1.length > 0){    
         this.attachmentService.upload(data.attachmentType1, 
            "type1", newItem.id).subscribe(newAttachment=>{

         });    
    }    

    //attachment type 2s 
    if(data.attachmentType2.length > 0){    
         this.attachmentService.upload(data.attachmentType2, 
             "type2", newItem.id).subscribe(newAttachment=>{    

         });    
    }    
    });    
}

Answer 1

最好的方法是使用mergeMap和merge和last来获得合并的最后一个发射值。你必须确定在of()内放什么。如果你从undefined调用返回一个对象，那么这应该是void 0 / null / upload;如果你从上传返回一个数组，那么应该是一个空数组[]：

createItemWithAttachments({ item, attachmentType1: type1, attachmentType2: type2 }): void {
  this.itemService.insert(item).pipe(
    mergeMap(({ id }: Item) => {
      const mergeUpload = [
        ...(type1.length ? [this.attachmentService.upload(type1, "type1", id)] : []),
        ...(type2.length ? [this.attachmentService.upload(type2, "type2", id)] : [])
      ];

      return mergeUpload.length ? merge(...mergeUpload) : of([]);
    }),
    last()
  ).subscribe((newAttachments) => {

  });
}

Answer 2

我认为有多种方法可以解决这个问题，但有一种方法可能是这样的：

this.itemService.insert(data.item)
    .pipe(
        take(1),
        mergeMap((newItem:Item) => {
            const attachmentUpdateObservables = [];
            if(data.attachmentType1.length > 0){
              attachmentUpdateObservables.push(this.attachmentService.upload(data.attachmentType1, "type1", newItem.id));
            }

            if(data.attachmentType2.length > 0){
              attachmentUpdateObservables.push(this.attachmentService.upload(data.attachmentType2, "type2", newItem.id));
            }

            return combineLatest(attachmentUpdateObservables);

        })
    .subscribe(newAttachments => {
        // Do something
    });