I'm currently in the middle of developing an iPhone app with a big reference database (using Core Data backed with a pre-populated sqlite database). Once the app is live and deployed to a client's iPhone, I need the facility to update/insert a small amount of data. What are best practices / methods for doing this?
There may be occassions when the frequency of updates will be daily for a month or so. Other occassions when a data update happens once every few months.
What is the recommended way of doing this? Note, I don't anticipate any data model changes for these updates -- this is purely an insert/update of data.
At the moment I'm starting to research the use of push data notifications (q:payload size restrictions?), app store updates (q:code/data model only, not data updates?) and the use of my own ad hoc data server (which the app connects to routinely to check for updates).
Can anyone please provide me any pointers on the above?
Thanks in advance
IIRC Push Notifications have a maximum payload of 256 bytes. Enough for notification purposes, but not more. Your app would still have to download the actual data from your own server after receiving the notification.
Note that the app bundle is not writable on the device. So if your app needs to update the data store, you should copy the pre-populated database file from the app bundle to the app's documents directory on first launch.
App Store updates would certainly be feasible (especially now that Apple seems to have gotten its review process down to a few days at most) but note that an App Store update will always replace the entire app bundle (code and data), so if your pre-populated reference database is big, the customer would have to download it in full every time.
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We have finished writing an iPhone App that uses coredata.
In further versions we plan to add an iPad App that is able to display the data collected by the iPhone App (and of corse modify, use it) to give more interaction possibilities to the user.
My question is: Is it possible to move existing coredata (of already installed apps on iphones) to the cloud and read that data out with an iPad application?
If yes: can you point me in the right direction of where to start?
If no: is there another alternative to access coredata created with an iPhone App with an iPad app?
When using Core Data's built in iCloud support it doesn't matter what kind of device you're on, only that the Core Data stack is initialized the same way. Any iOS device or Mac can use the same iCloud store, and data created on one can be read on another.
One crucial detail though: If you already have a data store and you add iCloud support, those pre-existing records do not automatically get migrated to the cloud. iCloud works based on transaction logs, and transaction logs are only created when you save changes. Existing data that doesn't immediately change generates no transactions, and therefore doesn't go to the cloud.
If you have existing data when you add iCloud, you'll need to migrate the data to a new data store to force transactions for those existing records. You can do this fairly easily using NSPersistentStoreCoordinator's migratePersistentStore:toURL:options:withType:error: method. It's not hard, but it's not always obvious that it's necessary.
To get started, I first suggest watching Apple's WWDC videos on iCloud-- especially WWDC 2012's session 227, Using iCloud with Core Data. Next, I suggest extreme caution, because as of today Core Data's iCloud support is still, shall we say, far from being the most reliable of Apple's APIs.
I have an iPhone (iOS) app that keeps data in a local SQLite database on each device. The app is used to manage a virtual bank account for kids to track their allowance, spending, savings, etc. (KidsBank and KidsBank Free). I am getting a lot of requests from parents to provide a sync capability between parents and possibly even their children's iOS devices.
I have considered several options, but all are tedious and non-trivial since this basically requires database replication or a new architecture. Any transaction on any device ideally should appear (sync) to all devices in the family (as immediately as possible).
Ideally, I would like the sync to be automatic & hands off
Options include
(1) Use of iCloud
(2) Use a direct network connection between devices (wifi)
(3) Use of a server side database and web service (JSON/RESTFul)
(1) iCloud
PRO: iCloud provides distributed file sync
CON: iOS 5 required, SQLite database files can not be synced via iCloud, classic database replication (and non-trivial)
Using iCloud is a strong consideration. Devices can write a custom transaction log to an iCloud file where there is one file for each device identified by a unique device ID. Global unique ids (GIDs) and last change timestamps are added to each table. All participating devices will write a unique device ID to a separate file in iCloud. Upon app launch or upon log file change, the app running on a specific device will load all transactions but not those generated on their own device from the files via iCloud. The last participating device to load the transaction will remove the transaction from the file. If the device is not the last participating device, it simply signs off on the transaction and allows the file to sync via iCloud. There may be better algorithms, but the basic idea is the same - using iCloud to push around change logs.
(2) A direct wifi connection will allow two devices to manually sych.
PRO: Not as complicated to manage the sync process
CON: Users must both select to sync from their apps while connected on wifi
(3) Move the entire database or manage transactions on a server.
PRO: Sync is no longer required
CON: Typical issues for a web-driven app. Would need to rewrite the database service layer (currently in SQL) to use a remote web service. Cost of running a server (I would use AWS).
Can anyone offer some experience in syncing SQLite between multiple devices? I'm leaning in the direction of using iCloud to push around transaction logs. I'm trying to minimize cost and complexity.
Moving to iCloud is probably the best solution, as it is proven and made by Apple. You don't need to worry to much about the iOS 5 requirement, as according to most stats over 90% use it. iOS 5 is free to upgrade to. You could then rename your old version as Lite, and continue without syncing.
Syncing is probably one of the hardest things you do.
One solution I made is that all changes to a database leave a log, with timestamp, uniqueid and couple of other things to make sure the transaction is totally anonymous and totally unique. I have made an extremely simple web service that has two operations, you can add transaction to it, so I sync whenever the user is on wifi, so I push all changes, receive a result from the server, then delete the transaction records as they are synced.
The other action is to fetch the records, send the timestamp of last sync, userid and other.
All data is sent using JSON and received as such. It can easily handle tens of thousands of users, running on a small Amazon EC2 server.
This is pretty much how iCloud works, but I made this solution before iCloud. Now I am going to iCloud, but probably need to keep the server running for 1 more year or so, depends on usage.
Hope this helps you.
After finding time to get back to working on the app and also with time passing and Core Data iCloud replication maturing, I converted my app to Core Data (NSSQLiteStoreType) and monitor notifications such as persistentStoreDidImportUbiquitousContentChanges. Using lightweight migrations too. Working well.
I have an app that uses an SQLite database. With the advent of iCloud on the rise I'm trying to figure out a good architecture for syncing data between devices. So lets say my app runs on an iPhone, an iPad, and a Mac. How can I keep data in my DB up-to-date on all devices?
My first thought was, I can put the database in the cloud and send transactions. But the device may not always been online and the users need their content at anytime, so that wont work. My other thought was to continue using the local db, and then when a connection is made, to send the cached data to the central db. The problem is I have no ideal where to even begin on something like that. How would I know which data has been sent and not sent, which data to actually send when a connection is made, etc.
So this is my question (we don't have to get into iCloud specifics), using an SQLite database and iCloud (or any storage medium), how can I sync data between multiple devices, but still have the most recent data stored locally on the device?
You might want to checkout Couchbase Mobile. This would help with the synchronization you are looking for.
If you have a significant investment into CoreData, then you may want to look at writing your own NSIncrementalStore to support writing data to and from a key value store.
iCloud is only going to be a good solution if your data is sandboxed to a specific user. If you have multiple users that want to view the same data then it won't work.
I am developing my first iPhone application and currently considering whether to deploy the app packaged with data, instead of calling upon a web service for the info. The obvious benefits are for those situations where you have a poor/non-existent connection and i could easily write something that could update the client data periodically from within the app.
What i am not sure about is how to store the data - sqlite, core data, plist or iphone file structure - Simply because i dont want someone unzipping the deployed application and getting their hands on the raw data.
Is this actually feasable? or is pretty much everything accessible once its deployed as an app?
You cannot stop somebody from accessing the data stored on the device, independently if you use sqlite, core data, plist or iphone file structure. At least not within reasonable means.
What you can do rather easily is to make the data useless for unauthorized access. In other words: encrypt it.
If what format you store the encrypted data then depends on the app needs.
This is pretty tough to do. The easiest way to do this would be by using the Xcode Organizer panel and then looking at the applications that you have installed. If it is one of your applications (matching your dev credentials) then Xcode will give you the option to download the application's sandboxed folders (docs, temp, etc).
From memory, you cannot do this to another application that doesn't belong to you. So in short you are safe to include data in your app. Honestly though, if someone wants to get to that data, they always will given enough time and resources (thats my opinion about all security).
I'm currently creating an iPhone app where in one part of my app you can view your twitter stream. I'm unsure if I need to ever save the twitter information to a sqlite database or not.
So here is the flow of this part of the app:
press button to see twitter stream
go get twitter stream
display twitter stream in table view
I'm wondering if I should ever save the twitter stream into a database. Any advice?
I would say you should save the twitter stream. You should almost always try to save some application state in an iPhone app. This way, if the user is interrupted (a phone call) they can jump back into your app without missing a beat.
There are a few different ways to persist data in an iPhone app. Instead of bothering with using a SQLite database you will almost certainly want to use Core Data, which is new in iPhone OS 3.0
If you won't ask the user to provide his/her twitter credentials and it will be an anonymous stream, you don't need to store anything.
But the minute you want to store some preferences, actual state (to show the user what he/she was seeing when a phone call came or after application restart) you will need to store persistent data.
I think it's important to cache web data. With a cache, you can present data immediately on app startup - this is important on the iPhone OS because users are constantly opening and closing apps. Having your data immediately available is a big win for the user.
You can make the caching very simple, just have a single table with the URL as one column and the HTTP response as a second. Then you don't have to change any of your code to make the caching happen.
Alternatively, you will need to define a data model and manage that through CoreData or sqlite.