UserResponse.swift

struct UserResponse {
    var _id : String
    var first_name : String
    var last_name : String

    init(JSON: [String : AnyObject]) {
        _id = JSON["_id"] as! String
        first_name = JSON["first_name"] as! String
        last_name = JSON["last_name"] as! String
    }
}

/* Inside our completion handler */
var user = UserResponse(JSON: response.result.value as! [String : AnyObject])