解析来自Apple Push Notification的数据

我有通过Firebase发送的推送通知，当用户执行操作时，会有一个php脚本将推送发送到关联的FCM令牌。收到了推送通知，但是我试图从“ gcm.notification.payload”键中获取信息。我尝试将userInfo强制转换为Dictionary，NSDictionary，[String：Any]，JSON，但没有任何效果。当我尝试说有效负载[“ type”]。string时，值为nil。这是我能够从有效负载字典中获取某些信息的最接近的地方，其中通知是收到的UNNotification：

let userInfo = notification.request.content.userInfo


let json = JSON(notification.request.content.userInfo)
guard let gcmNotificationPayload = json["gcm.notification.payload"].string else { return }
let payload = JSON(gcmNotificationPayload)
print("json \(json)")
print("payload \(payload)")
print("\(notification.request.content.userInfo)")

控制台输出：

  json {
      "gcm.message_id" : "0:1523811750249807%3990eb5d3990eb5d",
      "aps" : {
        "sound" : "default",
        "badge" : 1,
        "alert" : {
          "body" : "Tap to Open Herds List",
          "title" : "test4 test has added you to a herd!"
        }
      },
      "gcm.notification.payload" : "{\"image\":\"https:\\\/\\\/www.test.com\\\/images\\\/users\\\/417\\\/5acd085c97c3a.jpg\",\"type\":\"6\",\"title\":\"test4 test has added you to a herd!\",\"message\":\"Tap to Open Herds List\"}"
    }

    payload {"image":"https:\/\/www.test.com\/images\/users\/417\/5acd085c97c3a.jpg","type":"6","title":"test4 test has added you to a herd!","message":"Tap to Open Herds List"}

    [AnyHashable("gcm.message_id"): 0:1523811750249807%3990eb5d3990eb5d, AnyHashable("aps"): {
        alert =     {
            body = "Tap to Open Herds List";
            title = "test4 test has added you to a herd!";
        };
        badge = 1;
        sound = default;
    }, AnyHashable("gcm.notification.payload"): {"image":"https:\/\/www.test.com\/images\/users\/417\/5acd085c97c3a.jpg","type":"6","title":"test4 test has added you to a herd!","message":"Tap to Open Herds List"}]