可觀察認購，則返回響應，無法訪問域

Question

在這裏，這是我觀察到：

userLogin(formData: Object):Observable<Response> { 
    return this.http.post(apiURL + '/api/logon', formData) 
     .map((response: Response) => { 
      return response.json(); 
     } 
    }) 
} 

然後我訂閱，因爲這地方：

this.auth.userLogin(forData) 
    .subscribe((result) => { 
    console.log(result); // this logs the response from server object 
    // console.log(result.username) doesn't work WHY? 
    // Error: Property 'username' does not exist on type 'Response' 
    }) 

那我做錯了嗎？

編輯：

CONSOLE.LOG輸出該：

Object { 
    pappassword:"2f636cc3f8ffeda00dfe448fc483ce3" 
    success:true 
    uamip:"192.168.182.1" 
    uamport:"3990" 
    username:"jh" 
    userurl: "http://www.gstatic.com/generate_20" 
}