I would like to know if it is possible to create the file of a database by programming?
Actually I need to create a database if it does not exist.
I'll assume you have your own valid reasons for using sqlite3 directly rather than Core Data. There are certainly cases where it's appropriate.
The sqlite_3_open() function will create the database if it doesn't already exist. The sqlite3_open_v2() function will create the database if you pass SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE in the flags parameter. See the documentation for more details.
Of course on iPhone you'll need to make sure you're creating the database in a read-write directory such as the app's Documents directory, as opposed to the Resources directory, which is read-only.
In practice I've never tried building a database from the ground up on the iPhone. I always found it simpler to just include an empty DB file with the schema pre-built as an application resource, and then copy the file to the Documents directory the first time the app is run.
Are you sure that you need to create the database file directly? Maybe you should check out the Core Data Framework.
Thanks for your answers, I have never used Core Data so I will have a look on this.
For the moment I also copy a DB file from the Resource directory to the Documents but I would like to create a static library which can be used by many persons. So I would give a minimum of files to add to their project. That's the reason.
Related
I am a Swift newbie currently working on an IOS application, which needs to access an existing static database (size 400kb) of 1 table with about 3300 rows, and 26 columns. This database was initially a CSV file, converted into an SQLite file.
From forums I read online, it is to my understanding that SQLite queries are incredibly fast, and for that reason should be the preferred choice. I will only need to be reading the database and will not perform any writes.
I have found a number of old tutorials online which have utilized Objective-C or tutorials from several years ago which utilize swift 2 or 3. A newer solution I found was to use this SQLite wrapper: https://github.com/stephencelis/SQLite.swift. However, I am not entirely sure how to implement it. I was wondering if it was possible to read directly from my bundled database, or if I had to create a new table and copy from the bundled database.
It looks like SQLite.swift will get the job done for you. From the documentation on the page you linked it looks like you use Connection(pathToDB) to start using the library.
Since you're bundling the database and don't plan on modifying it you should be able to use Bundle.main.path(forResource:, ofType:) to get the path to your bundled database. If you want to modify it, you'll probably want to copy it to the documents directory and then reference that copy.
Another good answer on getting paths to various kinds of bundle resources if you need more help:
How to get path of image form Resource of main bundle
do we have any command line from where i can query the sqlite database, which is created by coding, and stored in the application's default Documents folder?
Turn on file sharing for the app, copy the database file to your Mac, and use the command line tools (sqlite3) that are there.
(Note to the previous editor: I appreciate editing of answers for accuracy, format improvements, and fixing typos...but, if you want to provide completely different information, I suggest providing your own answer instead of changing the meaning of another user's response.)
Can someone help me find where CoreData is storing the SQL file it creates in iOS applications?
So far I've tried "Show package contents" on the .xcdatamodel file and also the .xcodeproj file...No dice!
Is there an editor for looking at the contents of these SQL files?
Cheers.
-A
The url parameter of [NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:url:options:error] specifies the location of the file. Find this call in your code and see where you've stored it. XCode templates will put it into the top of your application documents directory, but you can put it anywhere you like.
Note that Apple considers the contents of this database to be opaque and non-user-modifiable. Playing with the data in your store is likely to cause issues with Core Data.
It's typically saved into your application's documents directory, with the name of your data model.
So, for example, if my data model is called AppData.xcdatamodeld, it will be AppData.sqlite inside my app's document directory. You shouldn't really need to touch the .sqlite file though.
Hope that helps!
Core Data editor --> http://christian-kienle.de/CoreDataEditor/
I have some general questions about iphone app updates that involves sqlite db.
With the new update does the existing sqlite db get overwritten with a copy of the new one?
If the update doesn't involve any schema changes then the user should be able to reuse the existing database with their saved data, right? (if the existing database doesn't get overwritten from 1 above )
If there are some schema changes, what's the best way to transfer data from the old database into the new one? Can some one please give me guidelines and sample code?
Only files inside the app bundle are replaced. If the database file is in your app's Documents directory, it will not be replaced. (Note that if you change files inside your app bundle, the code signature will no longer be valid, and the app will not launch. So unless you are using a read-only database, it would have to be in the Documents directory.)
Yes.
What's best depends on the data. You're not going to find sample code for such a generic question. First, you need to detect that your app is running with an old DB version. Then you need to upgrade it.
To check versions:
You could use a different file name for the new schema. If Version2.db does not exist but Version1.db does, do an upgrade.
You could embed a schema version in your database. I have a table called metadata with a name and value column. I use that to store some general values, including a dataversion number. I check that number when I open the database, and if it is less than the current version, I do an upgrade.
Instead of creating a table, you could also use sqlite's built-in user_version pragma to check and store a version number.
You could check the table structure directly: look for the existence of a column or table.
To upgrade:
You could upgrade in place by using a series of SQL commands. You could even store a SQL file inside your app bundle as a resource and simply pass it along to sqlite3_exec to do all the work. (Do this inside a transaction, in case there is a problem!)
You could upgrade by copying data from one database file to a new one.
If your upgrade may run a long time (more than one second), you should display an upgrading screen, to explain to the user what is going on.
1) The database file isn't stored as part of the app bundle so no, it won't get automatically overwritten.
2) Yes - all their data will be saved. In fact, the database won't get touched at all by the update.
3) This is the tricky one - read this fantastically interesting document - especially the part on lightweight migration - if your schema changes are small and follow a certain set of rules, they will happen automatically and the user won't notice. however, if ther are major changes to the schema you will have to write your own migration code (that's in that links as well)
I've always managed to get away with running lightweight migrations myself - it's by far easier than doing it yourself.
What I do is that I create a working copy of the database in the Documents directory. The main copy comes with the bundle. When I update the app I then have the option to make a new copy over the working copy, or leave it.
i am working on an application that displays read-only data i am shipping.
it is more of a book.
It is easy with SQLite but i am not satisfied with the performance and trying to use Core Data.
The issue is with pre-filling Core Data is that it is a hard process.
My question is:
Is it possible to build an assistant iphone application (for me to use) which uses the same data model for pre-filling.
and then take the populated .xcdatamodel file and use it in my original application?
I hope this makes sense :)
Adham
I believe what you're asking is whether you can create a CoreData database upfront and copy it to the iPhone. Is that correct?
This article will help. Here's a quote:
I thus suggest the following five-step process:
Create your data in a comma-separated file, typically placing each row of data (an entity) in a row of the file and separating different columns (its attributes) by commas.
Write a standalone program and copy in your .xcdatamodel file from your main project.
Write code in your new program that parses your comma-separated file and inserts the information into a Core Data persistent store that should be identical to the persistent store in your main project.
Run the program in the Simulator
Copy your data from the Simulator's documents directory into your actual project's bundle.
It's possible, I've done it. I made a desktop application to read from a CSV file using the code here:
http://www.mac-developer-network.com/columns/coredata/may2009/
I just had to alter the way the CSV part worked, and change the model.
I copied and pasted my model from the model builder into the iPhone model. (Clicked on the "grid" area, selected all, copied)
Then I took the sqlite database the desktop app produced (found it in Application Support, in the folder for this application) and put it into the resources folder
I made some code to copy the sqlite into the documents folder on the iPhone (if it wasn't already there) at startup, in the applicationDidLaunch method. It's possible that having it in the resources folder is no good. Even though you're using the database as read only, Core Data may want to write something to it. Not sure about this though..
I used the sqlite file in the documents folder in my Core Data set up.
The desktop and iPhone Core Data sqlite file seem to be exactly the same format. You can transfer one sqlite file to another application (iPhone to iPhone too) as long as they have the same data model. In another application, I used NSXMLParser to create the Core Data sqlite file, then transferred it to another app, both on iPhone using the Simulator.
Yeah, your data source can be whatever you want it to be. The other suggestions are good ones. Create a managed object model (.xcdatamodel) identical to what you want to use in your app. Read in the data from your file, create a new instance of your managed object and populate it from the file. Then save, and dive into the bundle in the iPhone Simulator and copy it over. This has the added bonus of being in exactly the format you need, with all the helpful metadata. Copy your object model and your managed object classes and you're good to go.
Note, though, if you really intend for it to be read-only, and you're using it at install, it will be installed in your finished app's bundle (under Applications/{SIGNATURE}/Myapp.app). If you intend to edit this database or allow a user to save to it, it's a better idea to copy it to the Applications/{SIGNATURE}/Documents directory where your user database lives.