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角可观察链

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我所做的是：

A   B   C   D   E   F
----------------------
2   4   6   2   5   7
3   3   6   0   6   8
3   6   5   1   6   8
5   0   1   1   1   5
1   2   2   0   1   5


WHY I AM Subscribing B to A,C-> B,because on change of A,B will change and on change of B -> C will change (its like excel) where there are formulas on each field and change of each field other field will change 
ObservableB[i] = ObervableA[i];

ObservableC[i] = ObservableB[i].pipe();

ObservableD[i] = obbservableC[i].pipe(
Map(res => res +1)
);

ObservableE[i] = ObservableD[i].pipe();
ObservableF[i] = ObservableE[i].pipe();

和

ObserveB = dropdown Observable
ObserveC = dropdown Observable
ObserveD = Dropdown Observable
ObserveE = Drop down Observable
ObserveF = dropdown Observable

Now:

ObserveA = ObservableA.pipe(
  map(val => 
  {
    //map only unique values of ObservableA to ObserveA
   }
  )
);

类似地，对于ObserveB，ObserveC，ObserveD，ObserveE，ObserveF

现在我想要的是： 在选择ObserveA或任何其他下拉列表时，其他下拉值应更改 例如，如果我选择

注意：下拉菜单为多选

DropdownA values selected : 2,3

因此，其他下拉列表值应自动重置（通过重置，我的意思是其他下拉列表的可用选项应更改为）

means for B dropdown available options should be : 4,3,6 

ObserveC = 6,5 (only unique values in drop down)
ObserveD = 2,1
ObserveE = 5,6  (only unique values in drop down)
ObserveF = 7,8  (only unique values in drop down)```



Is this is achievable ??
hyk123456789 回答：角可观察链

下面的代码怎么样？

exclude.pipe.ts： 

  @Pipe({ name: 'exclude' })
  export class ExcludePipe implements PipeTransform {

    transform(value: any[],...args: any[]): any {
      return value.filter(x => ![].concat.apply([],args).includes(x))
    }

  }

unique.pipe.ts： 

 @Pipe({ name: 'unique' })
 export class UinquePipe implements PipeTransform {

   onlyUnique = (value,index,self) => self.indexOf(value) === index;

   transform(value: any[]: any {
     return value.filter(this.onlyUnique)
   }

 }

app.component.ts： 

@Component(...)
export class AppComponent {

  observableA = of([2,4,6,2,5,7])
  observableB = of([3,3,8])
  observableC = of([3,1,8])
  observableD = of([5,5])
  observableE = of([1,5])
}

app.component.html： 

<ng-container *ngIf="observableA | async as A">
  <ng-container *ngFor="let item of A | unique"> <td> {{ item }} </td></ng-container><br>
  <ng-container *ngFor="let item of (observableB | async | unique | exclude :A)"> <td> {{ item }} </td></ng-container><br>

  <ng-container *ngIf="observableB | async as B">
    <ng-container *ngFor="let item of (observableC | async | unique | exclude :A:B)"> <td> {{ item }} </td></ng-container><br>

    <ng-container *ngIf="observableC | async as C">
      <ng-container *ngFor="let item of (observableD | async | unique | exclude :A:B:C)"><td> {{ item }} </td></ng-container><br>

      <ng-container *ngIf="observableD | async as D">
        <ng-container *ngFor="let item of (observableE | async | unique | exclude : A:B:C:D)"><td> {{ item }} </td></ng-container><br>

      </ng-container>
    </ng-container>
  </ng-container>
</ng-container>
angularangular2-observablesasynchronousunsubscribe
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