Data driven view iOS app

I am new to objective-c/cocoa programming. I am making an application which is to constantly sync with a server and keep its view updated. Now in a nutshell, heres what I thought of: Initiate an NSTimer to trigger every second or two, c开发者_如何学Contact the server, if there is a change, update the view. Is this a good way of doing it? I have read elsewhere that you can have a thread running in the background which monitors the changes and updates the view. I never worked with threads before and I know they can be quite troublesome and you need a good amount of experience with memory management to get most out of them.

I have one month to get this application done. What do you guys recommend? Just use an NSTimer and do it the way I though of...or learn multithreading and get it done that way (but keep in mind my time frame).

Thanks!

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I think using separate thread in this case would be too much. You need to use threads when there is some task that runs for considerable amount of time and can freeze your app for some time.

In your case do this:

1. Create timer and call some method (say update) every N seconds.
2. in update send asynchronous request to server and check for any changes.
3. download data using NSURLConnection delegate and parse. Note: if there is probability that you can receive a huge amount of data from server and its processing can take much time (for example parsing of 2Mb of XML data) then you do need to perform that is a separate thread.
4. update all listeners (appropriate view controllers for example) with processed data.
5. continue polling using timer.

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Think about requirements. The most relevant questions, IMO, are :

1. does your application have to get new data while running in background?
2. does your application need to be responsive, that is, not sluggish when it's fetching new data?

I guess the answer to the first question is probably no. If you are updating a view depending on the data, it's only required to fetch the data when the view is visible. You cannot guarantee always fetching data in background anyway, because iOS can always just kill your application. Anyway, in your application's perspective, multithreading is not relevant to this question. Because either you are updating only in foreground or also in background, your application need no more than one thread.

Multithreading is relevant rather to the second question. If your application has to remain responsive while fetching data, then you will have to run your fetching code on a detached thread. What's more important here is, the update on the user interface (like views) must happen on the main thread again.

Learning multithreading in general is something indeed, but iOS SDK provides a lot of help. Learning how to use operation queue (I guess that's the easiest to learn, but not necessarily the easiest to use) wouldn't take many days. In a month period, you can definitely finish the job.

Again, however, think clearly why you would need multithreading.