this is no longer relevant since iOS4+ - so please stop downvoting! or at least explain your downvotes
I am trying to do an upgrade path for a lite to full version of an application, that can store an indefinite amount of data (I dont want to do in app purchase).
I would like to be able to upgrade using a custom url without needing an online presence to cache the data to.
So was thinking of using a UIPasteboard object.
Does anyone know, or done any investigations on the max possible size of data stored to a UIPasteboard? There seems to be no apple documentation, that i can find, regarding this.
Will this vary from device to device? i.e. is it RAM limited?
I tried a 50MB file and know this fails (even in simulator) though a 5 MB file is OK. There is no way of knowing if it has failed until you come to get the data with dataForPasteboardType:
Also, has anyone done 2 app custom URLs that will do a kind of request/response inter app comms? I was thinking that i could support arbitrary sized data this way...
I'll answer my own question, after doing some investigation, it's 8MB. Device independent.
I have also managed to support upgrade of arbitrarily large amounts of data using 2 custom URLs and the openURL method recursively between apps. Tested up to 100MB - it doesn't look too pretty because it opens each app 12 times!
I'm surprised there's any limit. I don't see why/how there would be. You give UIPasteboard a dictionary with a retained pointer to your data. Who cares how big it is? I suspect if you are detecting a limit, it is really a limit on the size of an NSString, or NSData or whatever it is you're supplying to UIPasteboard.
Related
I want to know what is the best way to store data on the iPhone from a web service.
I want the information to be stored on the device so the person doesn't need to access the web service every time he/she needs it. The currently information isn't much and contains less that 150 records. The records might update from time to time and a few new ones will be added. What is the best way to go about storing the data?
Thanks
If you use ASIHTTPRequest for your network stuff (and if you don't already, I can't sing its praises highly enough), you will find it has a cache layer built in which is perfect for situations like this.
You can activate it with a simple one line;
[ASIHTTPRequest setDefaultCache:[ASIDownloadCache sharedCache]];
And you have full control over the cache policy etc - just read the documentation.
The other simple approach of course is - on the assumption that your web service is returning JSON or XML - simply to store the response in a local file against a hash of the request parameters, then when you request the data again, you can first look to see if the file exists and if it does, return that data rather than going back to the website. You can roll your own cache policies etc too.
Since I discovered ASIHTTPRequest had a cache though, I've not needed to roll my own again.
I find that using coreData or sqllite3 is just overkill for 99% my requirements and a simple cache works very well.
If the data is relational, a Sqlite3 database would be the best storage option you have.
Also, this helps by allowing you to retrieve from the server and to update only the records that have changed, thus saving time and bandwidth.
This is the best option from a scalability point of view as well, as you stated that "current information isn't much", thus giving the impression that this is only a current situation, that may be subjected to further change, probably towards more records being added in time.
Sqite3 also gives you more control and better performance than using, for instance, Core Data. Here's an article explaining some of the details. Moreover, if you work through an Objective-C wrapper, such as FMDB, you get all the advantages without managing the complexity yourself.
I'm using MonoTouch and also System.Data to create a DataSet (just xml to those not familiar) for simple data binding. Data on my app is minimal so no need to go all out with SQLLite. The dataset use makes it easy to pass via web services for cloud sync.
I serialize the DataSet to the personal folder on save and of course read this file when the app starts up to load up the user's data. I've had issues where this file is becoming corrupt and I'm not sure why. I assume file I/O may be slow on these devices and that could be the cause, I'm not sure, but it is happening.
I'm also concerned that maybe iTunes is passing this file back and forth between the PC/MAC when the user syncs their devices with iTunes, which may be the cause of the corruption?
I want to prevent this device file from syncing with iTunes and also reliably persist it. I'm using the NSFile.Save option to save it to the device. I'm thinking since it's a text file maybe I could more safely store it in the standard user settings area instead? This would prevent it from being synced by itunes, I presume?
What is the most reliable and safe way to handle this file i/o for the xml dataset storage?
Thank you.
You're using MonoTouch. Isn't it simply a matter of calling DataSet.WriteXml() with a FileStream object ready to write to a document in your Documents folder?
That Documents folder is backed up to iTunes. It's not synced, but it helps if your user is restoring their phone (because they bricked it, lost it, whatever). It doesn't explain why it's corrupt.
The only thing that I can think of why it's corrupt is because it took too long for your app to write it. There's a limited time from the point where the user exits the app until it's closed down, to prevent apps from keeping the system hostage and deteriorate user experience.
If writing the whole dataset takes too long, you want to think about minimizing that. Perhaps you can just store the data, and not the schema. Or you can devise a way to store only the deltas on exit and reconcile when the user has loaded your app again.
You can also prevent complete loss of data by writing to a second file, and when that operation completes delete the old file and rename. That way, the next time you start up if the write operation didn't complete, the old file would still be there and the user would have only lost their more recent changes.
In any case, if your data gets too big for a simple write operation to complete, you should look at different options such as sqlite.
Your best bet is probably to just save the XML as text. It's as simple as File.WriteAllText(...) - there's no reason to go to NSFile for this. That's part of the advantage of MonoTouch :)
Regarding syncing, here's the rule:
If you keep the file in the user's documents folder (Environment.SpecialFolder.MyDocuments and Environment.SpecialFolder.Personal BOTH point to the user's doc folder), then it's going to get backed up whenever the user syncs with iTunes.
There's nothing wrong with this. It persists the data between sessions and makes it recoverable if something goes wrong with the user's phone and they need to restore from a backup. Since your question is about persisting an XML file on the phone, this is what you want.
As for the iTunes question, there's no problem with speed and syncing because your app isn't going to be running while the phone is syncing. The file will either have been saved or it won't. Any corruption that takes place is happening while your app is running.
Reasons for files getting corrupted can include:
Not saving before the user quits. You get a chance to do this.
Not gracefully handling an incoming phone call. The system warns you about this as well.
iTunes definitely isn't corrupting your file. If that were the case, iOS apps would all be broken. It could be happening on your dev machine for whatever reason, but I've never seen this happen elsewhere, and I've done quite a bit of iOS development.
If you'd like a tutorial on reading and writing files, I posted an answer in another question.
It's lengthy, but the point was to answer as many questions as I could so nobody would be left hanging or confused.
A nice thing about iOS devices is that you're back (for most apps) in the one-person-at-a-time world. You're writing apps where you don't have to worry about 5,000 people trying to use your web-based app at the same time (that's not always true, but... you get the point). As a result, you can do things that you might normally consider bad for performance, but you're unlikely to see any performance problems (as long as the file you're saving is either small enough to be saved quickly or you're saving in the background on another thread - you never want to block the main (UI) thread with a heavy IO operation).
If you have any more questions, feel free to ask.
I hope this helps :)
Lots of frameworks are read-only, but I've found that GDataXMLNode from http://code.google.com/p/gdata-objectivec-client/ works very well read/write.
Having said that, on the iPhone you'd do yourself a big favour using Core Data with a SQLLite backend. :-) Apple has done all this for you and optimized it more than any of us every will
Cheers
Nik
Consider using SQLite, I'd go for something like
http://www.taimila.com/entify/ (not tried yet)
catnap orm
or Faks sqlite-net on google code (using this in a few apps)
entify - if it does what it says it can do - looks really good.
persisting XML on the iPhone as a means to store and access data is a nause you dont want to get into. I wrote about it here http://iwayneo.blogspot.com/2010/08/festival-star-history-serialization-as.html
I need help with downloading from webserver...
What i currently do is get XML file from web servers that contains image locations, parse XML, download each image, store image on iphone, and store image name to sql database.
This takes lots of time because there is large amount of images to be downloaded and i am downloading one by one.
My app update just got rejected because reviewer decieded that downloading is too long... What is funny, last two updates passed without problems..
I was thinking about zipping those images on server and sending zip file to iphone, unzipping it there, or packing images together with binary and sending it to apple.
Any advice on how to make download faster, would be appreciated. Thanks.
BTW, zip won't help with images. They are already compressed, so it will just add overhead. Make sure your images are not any larger than you need for display and I'd do what Mario suggested above and download them in multiple async calls (at least make the one big call asynchronous.)
A key principle of UI design is to display partial results (unless they are invalid or misleading) so that the user understands that progress is being made.
If you really need all the images to make it valid, you can download a few and display them grayed out (alpha = 0.4) or something so that it's clear that this is a partial result, but that progress is being made. The reviewer probably felt that it was taking too long to startup.
Do you change those images often? Or only once per release if at all? If they change with each release only I'd package them. If they're almost never changed, go with the one huge download (so people don't have to redownload when updating) and if they're change often, download them file by file but try to do 2-3 files at once using asynchronous download (if supported).
1) I would use something like an NSOperationQueue to download around three images at a time in the background. Much more than that and the UI starts getting choppy.
2) Also display some kind of loading indicator while this is going on.
3) What format are your images in? If you are transferring over the network you should use JPG, and consider setting the quality level to something smaller (say 6 even 5). To offset the loss of quality you could send down larger images, even with the larger number of pixels you can easily be better off with a lower quality compression.
4) If you have to use PNG to preserve transparency, consider using PNGCrush on the images before sending. As noted, zip will do pretty much nothing.
One way to speed up download of those images is to put them on a CDN. Some CDNs, like Limelight have special network optimizations for sending data to mobile devices. They also just do a better job of routing content, and have higher capacity for transmitting content. What's nice about this approach is that you might not have to change your app. However CDNs can be pricy.
Likely, your images are just way too large. You said you're worried about the 20MB app limit, but I think at that point, your images are just way too large for the phone.
Rather than zipping the files, I'm pretty sure you need to downsample the size of the images. Not only that, but you should only download the ones that you need, when you need them.
If you still want to have bulk downloads, why not have it as a side option rather than the default implementation?
Okay, I want to have an app that takes phone numbers from an online database and displays them in a table view. When the user is not online, I want them to still be able to see the numbers they already got from the database in the table view. If the user manages to go back online, the database updates the view. My question is, is this possible to do and if so, what's the best way to approach it? (bit of a newbie, please help me out)
There are many ways to do what you are asking, depending on the complexity of what you are after.
Could I suggest the following steps (I'm not sure which ones you can do, and which ones you are having trouble with).
Connect to the server and retrieve the list of phone numbers
If the database has a web server front end this might be as simple as sending a get request to the server (see NSURLConnection) and parsing the result. Otherwise you will need to know/tell us what type database you are using.
Store the phone numbers on the device
Use SQLite to store the numbers on the device (See iPhone SQLite Resources)
Check for internet connectivity
Periodically check for internet connectivity, and if a specific time has elapsed since you last polled the server, retry. (See Checking iPhone internet connectivity)
Although you’re probably looking for a native app solution, you can also do this with a web app.
http://diveintohtml5.ep.io/offline.html
I am a new developer iPhone developer, "learning" to be precise. I came across the useful NSUserDefaults (a dictionary in which you can store/restore state even after your application relaunches). Problem with this dictionary will be memory in your case. NSUserDefaults is sort of global to all applications and yours may spoil the show for other innocent applications (like Weather :D ).
To work around this, you can have your application declare a property list file where you store a few numbers (best practise would be the most recent but you can use any selector of choice). Look for an appropriate time in your run loop to store these numbers into your property file and load them when the application starts.
I have created an app which displays information in a organized manner about cultural places.
The information is subject to changes, so I want it to be downloaded from the web. But not everytime. Only once in a while, because information doesn't change often.
What I want to do is, the first time the user opens the application, it downloads all data from the web. For the moment, I parse it from an xml (which is about 100Ko), and I get a NSMutableArray of "CulturalPlace" objects. but it is very slow. And what I would like to do is, to store this data locally (in case the user has an iPod touch an is not on a wifi, or if he is on EDGE and does not want to redownload all). So the user updates data only by clicking an "update button" on the top right of the screen. Otherwise it reads it from disk.
I really don't know what could be the best solution. I thought about Core Data, but I have several Tableview imbricated (Rootviewcontroller > ListofPlacesViewController > PlaceViewController) and I really cannot find good tutorial for a simple use like mine. (the iTunes "TopSongs" sample code seems too complex).
I thought also about not parsing the xml, but instead try an NSURLConnection and get a plist file. But I never managed to read anything from the local file.
So my main question is, should I keep the xml parsing method, or should I use another format to tranfert the data from the web? And what is the best way to store and read data like an NSMutableArray of custom Objects ?
Thanks in advance for your help, sorry for my approximate english.
You could use HTML5' localStorage. It's supported by Chrome and FF on the PC and Safari on Mac OS and iPhone (to the best of my knowledge). It acts like a local database. Bear in mind that if the user selects to clear all cookies (or "private settings"), your storage goes away.
You could opt to store the XML locally, and store in NSUserDefaults the date when last updated - then on app launch you can check to see if you have a new file.
ASIHTTPRequest makes it pretty easy to say "Save the contents of this URL to a file". So you'd always save the XML to a file, and always read from that file or fetch XML if it was not yet there.
In my experience XML is indeed much slower to parse than plist, even though they're technically the same thing. Fortunately, plist's are pretty easy to deal with and the API's take care of all of the archiving and de-archiving.
Once you have your data in memory, it probably wouldn't be too hard to convert it to the much faster plist representation, check out this doc for more info: http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/Archiving/Archiving.html
If your app is divided into different pages, you might also consider splitting the file into separate files, and only parsing / de-archiving the information you need when you need it (if you did this on a separate thread and displayed a UIProgressView on the main thread, the delay would probably be barely an issue to the user).