Ive made an enterprise Universal (iphone/ipad) app that uses the odata sdk to talk to an sql server database. All great, works fine. The issue (well not really an issue, but somewhat of limitation) is that it is a connected solution, if you want to retrieve or update information you have to be connected to the internet.
Im now trying to add disconnected functionality. My question is, is there a way of saving large (relatively large) amounts of serialized data to the actual device. I dont want to store it in the application because
- it will build memory up in the app really quick
- if the app crashes they will lose the data
Any ideas on how I can go about this?
Use Core Data... Apple has very good documentation, check it out!
It sounds like you want to synchronize data between an online system and the device. Synchronization is a very difficult problem to get working perfectly. If your web service is REST compatible I would look into RestKit as a solution for communicating with your online system and storing that data in Core Data locally on the iPad.
Ultimately you want to replicate the data online with a database locally, I would recommend Core Data for this if it is a large amount of data. Core Data alone is a complex framework and will require a good amount of understanding.
There are a lot of things to consider, how much data is needed offline? Can you perform delta syncs? How is data moved around and what steps are necessary for moving the data in the local database when moves occur remotely? How do you detect that a record was deleted online and therefore needs to be deleted locally? Can you users edit existing data while offline? What do you do about merge conflicts (same record is edited online and offline)? You will want to think about all of these scenarios.
There are some systems out there that can handle some of this for you, if your online system is also in development you may consider CoucheBase which has a mobile counterpart that handles this tricky synchronization problem for you.
Good luck!
Core Data is the way to go.
http://developer.apple.com/library/mac/#referencelibrary/GettingStarted/GettingStartedWithCoreData/_index.html#//apple_ref/doc/uid/TP40005316
