I am trying to write an iOS app that will notify the user on price changes of products I access as JSON information via an API. I want to have a background task that will repeatedly check the server every n minutes for new JSON and send the user a notification if certain conditions are met. What would be the correct way to do this?
As previous posters mentioned, this is better done server side rather than via polling. However, using Apple Push Service to notify the client device is not the ideal solution. The issue is that delivery is not guaranteed (per Apple) and you cannot confirm delivery. The user could decline push notifications, Apple could decline to send the notification if you are sending too many, etc. You are much better off using a service like PubNub or Pusher, which push notifications to the client in a reliable way and both have iOS APIs. They are very inexpensive. If you wanted to reinvent the wheel and save money, you could look up how they work and write your own version.
You could of course do client side polling, in which case an asynchronous NSOperation is particularly well suited (it will run on a background thread and you can post notifications to NSNotificationCenter when things change). You can find out more about how to implement that here.
This does not work well. Here is a probably better solution:
Set up a server that polls the JSON data source.
When the data source changed, use Apple Push Service to notify the user.
Upon receiving of the notification, start a background fetch session.
Related
I am writing a messaging app in Swift where people can chat similar to how text messages or other popular chat apps work. The supporting API is on AWS, written in C#.
There are some points of interest here:
Hoping to avoid third party stuff like Firebase, etc, but open to listening to advice
Alert notifications are not desired for now - no popups, banners, etc. Simply want to show message bubbles arrive in real time on one viewcontroller - if and only if the person is staring at the message screen. If they're somewhere else on the app, nothing happens.
We don't want to prompt the user to ask them if they're OK with this app sending notifications because we're not sending them banners or anything visual, aside from a new chat arriving. Is that a requirement with APNS? I feel like this means someone can say NO, and then we have no way to update the chat app in real time, which won't fly.
I assume a simple approach would be some sort of timer/loop that runs from the message viewcontroller, where every second or two it hits the API and asks if there are new messages, but that seems inherently wrong to me - the app must be robust, and there could be thousands or hundreds of thousands of people using this - that's a lot of API requests, and in many cases there could be no new messages, thus a wasted call. This is clearly not the way to go, correct?
Question # 1
I was thinking, then, that I should use APNS, however am not sure if it requires you to prompt the user to ask them for permission to receive anything from Apple? Again my concern is the chat bubbles should come in at real time and don't want to give the user the ability to somehow not see these (breaking the app)
If APNS is the way to go, and I must prompt them, then I assume the flow is I will gather my device ids (created in appdelegate, saved in my C# db, and associated to each message thread) and whenever someone types a message, it goes to my API, I save it in the message database table, and then I send out a message to APNS to everyone's device id.
Apple queues this up, and sends to everyone, and if they're on the screen, then the message comes in.
Is this how I should leverage APNS to achieve what I want?
Question # 2 I've seen others recommend using SNS (in conjunction with APNS) however I don't understand why. Doesn't APNS both act as a proper queue, as well as a notification service, thus invalidating the need to use AWS's SNS/SQS at all? It seems redundant to me but maybe I just don't understand the idea behind why you need both technologies.
Appreciate anyone's time in advance if they can shed some light on this for me!
Thanks!
Question 1
Even if you're using WebSockets (As #stevenpcurtis mentioned), you still need to inform user about the fact that user received message when application is in background/suspended. And yes, you must "force" your user to enable notifications for the application and explain why he needs it. Empirically, if user installs messenger, he understands what are notifications used for and why he enables it.
Question 2
From the mobile perspective SNS will still deliver Push notifications when user receives notification while the application is in background or suspended. From the backend perspective you can use SNS.
Conclusion:
From the mobile perspective you have 2 modes:
Application is active - it's generally up to you how to receive messages. (Web Sockets, pushes, e.t.c.)
Application is in the background or is suspended: You need a tool to inform user about changes without having a control on application. This is the job for Push Notification Service. The way you will send pushes from the backend is up to you.
You can also check This question to get some more information.
Im using restkit and push notifications and I have also built the interface, so here is my question I wanna know your opinion on how to build the structure of a chat app with restkit.
Should I update the incoming messages every 5 min ? OR
Should I update when I receive a push notification ? OR
AND
should I use the restkit queue to do this?
Should I use restkit core data ?
So, I guess my question is the best way t ask the server new messages.. so what is your recommendation???? mmmm... is there any example or framework ??
THANKS!!!
If you're building any sort of chat application, your users will expect that their messages are received immediately. I will assume that your server dispatches a push notification as soon as it receives a message. You should poll the server for new messages when the following events occur:
A user launches the app.
The application resumes after being suspended to the background.
The user launches the app in response to a push notification. (probably the same code as 1).
The application receives a push notification while it is active.
If your server reliably sends push notifications when an event occurs, you shouldn't need to manually poll.
You shouldn't need to directly interact with the RestKit Request Queue for something as trivial as this. RKClient can safely manage it for you.
Remember that the user will expect the app to handle network reachability issues well. The request queue will do reachability tests for you and appropriately queue requests until the network is available, however you may need to listen for notifications and provide an appropriate response. To do so, you should register for RKReachabilityStateChangedNotification NSNotificationCenter notifications posted by the RestKit framework. You may also need to save unsent messages locally and retry them later, especially if the application is suspended/terminated.
Remember to keep track of some sort of unique identifier you can use to tell the server what message you most recently acquired. The server should then send you an array containing every message after that point.
Finally, Core Data is a great way to store data that must persist between launches. With RestKit (and inherently with core data) your data is conveniently available as a collection of objects, and you can perform powerful queries against this data.
i m making an application where data is accesed from website and displayed with an application.i have made an action which will tell the user that new data has arrived.this will work properly if the application is open .but if the application is closed than ,is there any way to tell the user that new data has arrived ,,so that he can open the application and check the data?
If you are using the Apple Push Notification Service (APNs), your messages will be delivered whether the application is running or not. For information on how to control what information is presented to the user, read the Apple Push Notification Programming Guide.
You should use Apple Push Notification Service, like codelark said.
I would recommend looking into Urban Airship for help getting started. It's a third party service, but it makes things much easier. Urban Airship does have their own tutorials and code samples which may be easier than Apple's.
As a follow up to the reference to apple push notification, as of ios4.0 I believe you, you may have a few more options, 1) you can send local notifications (just like push notifications, but they originate from inside your app) that could be timed to be delivered even if the app is not running..assuming you know approximately how long it will take for data to arrive. 2) if your data update will occur soon after the app closed.. your app can request a certain amount of time to complete an operation (even though the user has closed the app) and wait for the data, then send a local notification to tell the person to come back into the app. 3) if your functions based on gps updates, music streaming, or voip you can set a flag so your app continues to run in the background
sorry for the unstructuredness of the answer, this was just off the top of my head, hope it helps
How are push notification better than pull notification on iPhones?
Are there any links with more information about this?
Any help would be appreciated.
Pull notification requires the user to be running your app, and your app to be wasting battery power constantly polling some server (or waiting on some network socket in another thread , or using the new background services).
Push notifications, when enabled by the user, and if the phone has a network connection, allows a message to be sent to a phone even when it's not running your app, prompting the user that your app wants some attention. It uses a much lower power network connection than any frequent polling method.
If you want to know about push notifications, I'm guessing you are interested in the Apple Push Notification Service.
You can read about its architecture here:
http://developer.apple.com/iphone/library/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/ApplePushService/ApplePushService.html
There is no such thing as a "pull" notification, but using APNs gives you the advantage that you don't have to manually poll a server every so often within an app, which usually saves you a lot of battery life in the long run if you are interested in telling the user about sporadic, infrequent events. Using push notifications also allows you to interrupt the user if they are not currently running your app, which of course can be very useful in certain use cases.
You should think about what kind of message flow you expect to see between your app and any server components in your system. Push notifications make the most sense where some event external to your app is going on which requires the app to be updated in some way, and where the frequency of those updates is low or highly variable.
I'm doing research for making a chat based app for the iPhone (it's not really text chat in the regular sense, but the principles are the same).
Maximum 6 people can be logged into the same chat room at any one time, and the most basic question is how to efficiently check for new messages?
Would I need to simply poll the server periodically? Or is there a way I could trigger an event on the phone from the server whenever there is some new content to pay attention to?
If having to poll all the time, I worry about the resulting lag as each participant will have to wait longer for others before they can post their own responses to others. And, potentially it might also be too much to handle for the server to respond to lots of requests all the time. It would also waste bandwidth, which is not free for the user...
Unfortunately I will not be able to set up a socket server for this app, it has to be based around a regular LAMP configuration.
I think you can either go with push notifications, or XMPP (Jabber) server.
XMPP will allow your iphone app to receive data even when in the background using the new multitasking features (listening for a socket), and i'm pretty sure you should find ready to use servers for LAMP (or at least open source implementations).
Note that the iOS4 multitasking API doesn't support polling in the background, so your only other option should be push notifications. If you're new to push notifications, you can maybe use a service like Urban Airship that might make the process easier.
XMPP sounds good for you idea, i think this is the best technology for Chat. It alos works great in iOS apps.
Maybe this code sample will be helpful to start using XMPP in iOS app - look at this QuickBlox Chat code sample. It demonstrates how to integrate 1-1 Chat, Chat in room into your android application. Also there is guide how it works. I think there will be no problem to integrate it into your application. Otherwise - Comments system below allows to ask any question you want and get fast answer.
Also there is Demo video http://www.youtube.com/watch?feature=player_embedded&v=SncQaJBBW_0 how this Chat works.
In my opinion the best solution is socket, but you say that you can't implement the server side for this.
You could also implement it with push notifications. You can receive the push also when your app is running and send all the data you need inside the push. Usually chat messages are short...
If you don't want to mess with push notifications on the server then the only thing left, as long as I know, is the polling.