HTTP call using Observable not working

问题:

In the function below, I have two calls to the server, one using Observable and the other using Promise. The call using Observable does not reach the server but the one using promise does. Any idea why?

public placeOrder(order:string) {

//Using Observable
this.http.post(this.newOrderUrl, {order: order}, this.options)
.map((response:Response) => {
  console.log('new order', response.json())
})

//Using Promise
this.http.post(this.newOrderUrl, {order: order}, this.options)
.toPromise()
.then((response:Response) => {
  console.log('new order', response.json())
})
}

回答1:

You need to return the response.json() if you are using Observable

 return this.http.post(this.newOrderUrl, {order: order}, this.options)
   .map((response: Response) => response.json()
 );

and in your component, call using subscribe()

this._myservice.placeOrder('somestring').subscribe((orders: any) => {
});