I am developing an iPhone app which retrieves information via NSUrlRequest and displays through UIWebView.
I want to hold initial data (such as HTML pages, images) as a cache so that users of my app can access to data without network costs at the first time.
Then, if data on my web server are updated, I would download them and update the cache.
For performance issues, I think it is better to store data on file system than on core data.
Yet, I think it's not possible to release a new app writing data on disk.
So, I am about to store initial data(or initial cache) at Core Data, and when users launch my app for the first time, I would copy the data to disk (like /Library folder).
Is it, do you think, a good approach?
Or,...hmm, can I access to Core Data using NSUrlRequest?
One more question,
I might access to file system using NSURL, which is the same as to data on the Web. (right?)
My app would compare version of the cache with version of data on my web server, and if it's old, retrieve new data.
and my app will access only to file system.
All data are actually HTML pages including script, and images. And, I want to cache them.
could you suggest a better design?
Thank you.
Is it, do you think, a good approach? Or,...hmm, can I access to Core Data using NSUrlRequest?
No.
One more question, I might access to file system using NSURL, which is the same as to data on the Web. (right?) My app would compare version of the cache with version of data on my web server, and if it's old, retrieve new data. and my app will access only to file system. All data are actually HTML pages including script, and images. And, I want to cache them.
Yes.
But you could also be more clever. And by "more clever" I mean "Matt Gallagher." Take a look at his very interesting approach in Substituting local data for remote UIWebView requests.
Related
I'm starting to work on an app which will include in quite a few places data that I will download from my server each time user is asking to view them. Then, when user opens app again without any internet connection, app should let him view any content it previously downloaded, just loading it from the cache. The point of this is that the content changes from time to time and user needs to be able to see the last downloaded version if he can't connect to the server.
Problem is, I can set the cache to a certain size on disk, but I have to store ALL the content no matter the size. I suppose I'd have to set cache disk size to make it bigger when it's running out of space. What is a good way to do this?
P.S. Not sure if this is relevant, but I was thinking about trying AFNetworking for this project (previously I used ASIHTTPRequest).
If you're using NSURLCache as an on-disk cache, you can check the disk usage with currentDiskUsage. If this is approaching diskCapacity, you can increase it using setDiskCapacity. You should perform this check before you attempt to write to the cache.
I have worked on same type of project, I used AFNetworking and according to me storing the data in local database is better option then caching it... and at the time when user starts app just have one service call which just checks the database version. If its old version replace database and handle the case if network fails by displaying the older version.
I want to have on-the-device database for my iphone app. It concerns with the data, which comes from dictionary consisting of 200.000 things and their definitions. It is only related with text-type data as appeared. My questions:
1- Does SQLite hold all of these data?
2- When the client downloaded my app, he/she will also have the db in his/her device. Does app store allow me to update my app's db and upload my new release? (i don't know these issues well by the way)
3- And can any client, who downloaded my app, hack and obtain my database? Is there any prevention methods? Is SQLite resilient enough against these?
1- Does SQLite hold all of these data?
Yes, SQLite can cope with this amount of data.
2- When the client downloaded my app,
he/she will also have the db in
his/her device. Does app store allow
me to update my app's db and upload my
new release? (i don't know these
issues well by the way)
The general approach is to store the SQLite database in your application bundle and then copy the database into the application's document directory on the device when the application is first run. On subsequent updates to your applciation, you should check if the database within the document directory is the same version and update it if necessary. See the existing Run NSBundle from the documents folder question/answer for more information on this.
3- And can any client, who downloaded
my app, hack and obtain my database?
Is there any prevention methods? Is
SQLite resilient enough against these?
It's fairly trivial to open up an app (the deployment package is just a zip file after all), so yes, it will be possible to obtain access to your database data. Unfortunately there's no easy way around this that I'm aware of. (You could I suppose download the data from a server when you first run you app, but it'll still be accessible on a jailbroken device.)
Sometimes, you just have to bite the bullet and accept the fact that your data is going to be ripped off.
1) sqllite can definitely hold that amount of data.
2) You can put up an option of refreshing the database in your app. That can be used to sync the local db with the server copy. Updated db can also be added with the new version of the app.
3) You can encrypt your local db using SQLCipher for protecting your application db against hacks.
I have a iPhone app which loads json from my webservice.
I think its a good idea to store the data with Core Data but how should I sync the data with my webservice?
For example, say that I show a UITableView with the information stored in Core Data, and then I would like to update the object.
Are there any design patterns or ideas for this?
Each time your app loads it should try to load info from the web service. If it can't connect, use the local data. You should timestamp your data on the server and in the app so that you can track when the information was last updated. You can also offer a button to manually refresh the data. (Like the Mail app.)
EDIT:
To make asynchronous requests, you can see the ASIHTTPRequest library.
I want to develop a CRM iphone app. I think there are 2 methods to deal with the data store, one is using the Sqlite(but it can not share datas with others ?), the other method is using the webservice(let the app CURD data by one web application), I want to know which is better?
I think the question is not about having one or the other, you could have both: Webservices to expose a central server somewhere where common data is stored and your local SQLite database where a copy of this data is stored. This allows you for fast search etc. instead of contacting some remote server that may or may not be on-line.
If you want to share your data then you have to store your data in webdatabase otherwise store in sqlite
you can store your data in sqlite for fast access and when you want to share that time you can send it to webservice and retrive when you need to see more data
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).