Angular2條件switchMap和patchValue

Question

我有一個組件來創建或編輯旅行，我想要使用相同的形式。如果有任何參數，我如何提前檢查？

ngOnInit() { 

    this.trip = this.fb.group({ 
     id: '', 
     name: ['', [Validators.required, Validators.minLength(2)]], 
    }); 

    this.route.paramMap 
    .switchMap((params: ParamMap) => this.tripService.getTrip(+params.get('id'))) 
    .subscribe((trip: any) => { 
     this.trip.patchValue({ 
      id: trip.id, 
      name: trip.name 
     }); 
    }) 
} 

我已經嘗試過這樣的事情，但沒有成功

ngOnInit() { 

    this.trip = this.fb.group({ 
     id: '', 
     name: ['', [Validators.required, Validators.minLength(2)]], 
    }); 

    this.route.paramMap 
    .switchMap((params: ParamMap) => { 
     console.log(params.get('id')) 
     if(params.get('id')){ 

      this.tripService.getTrip(params.get('id')).subscribe((trip: any) => { 
       this.trip.patchValue({ 
       id: trip.id, 
       name: trip.name 
       }); 
      }) 
     } 

    } 

    ) 

} 

Answer 1

如何與此類似：

this.route.paramMap 
.filter(params => params.get('id') !== undefined) 
.switchMap((params: ParamMap) => this.tripService.getTrip(+params.get('id'))) 
.subscribe((trip: any) => { 
    this.trip.patchValue({ 
     id: trip.id, 
     name: trip.name 
    }); 
}) 

}