I'm trying create 2 apps, one that builds a persistent store, and another one that consumes it.
So far I have built one app that uses CoreData to successfully build a database from an XML file. So this project contains the data model, the .h/.m files for the entities, etc.
I'm now trying to enable the second app to read that .sqlite file by copying the data model file, the .h/.m files related to the entities and the sqlite file to that project (via add existing).
The code executes but always fails to find any objects in the database.
Are there any restrictions or correct steps to take when trying to copy over these files?
The solution here is deceptively simple.
Just copy your .xcdatamodel file from one project to another and then when you run your app in the simulator for the first time it'll create a Documents folder for the app. Just drop your saved .sqlite or .binary files into the yourApp/Documents directory on the device.
You can find the simulator directory in "~user/Library/Application Support/iPhone Simulator".
You can also download, edit, and upload the myApp directory on a provisioned iPhone by dragging and dropping into and out of the Organizer. Look at the Applications list.
The iPhone doesn't support xml stores with core data, only sqlite or atomic (binary). The sqlite store is by far the better option for most applications since it doesn't all have to be loaded into memory at runtime.
Is this what you meant?
I think (not 100 percent sure) in your app plist, if you set your application bundle name to the same thing, they will share resources because the device will think they are the same application...
I don't think this is going to work the way that you want it to. On the iPhone, each application runs in its own "sandbox", and it's not really possible for one application to write files that another can read.
Is it really two different projects, or is it two targets in the same project? That would seem to make a lot more sense, and then you can share entity objects as they change.
For copying core data files from one project to another, I first created a new project with core data support and then I opened the contents of the previous coredata file and except the root tag, pasted all child tags in the new core data file in new project.
Previousy I tried to delete the coredata file in new project, copy pasted the previous one and changed its name and it was not working.
Related
My app involves getting a large json file via the internet, and then parsing it into Core Data.
Thats fine, but how could I get the already filled version of this Core Data database into my app, so it is there when they first launch it. And the user can decide to refresh it later.
There's a reasonable tutorial about pre-loading over at Ray Wenderlich's site.
Generally - create a separate project, parse the JSON file into a core data database. Create your real project, copy the Object model and the database file to this new project.
Now, at app start up, check if the database exists in the document's directory, and if it does not, copy your prefilled one from your app bundle.
Make sure that the Persistent Store Coordinator works with the database in the documents folder and not the one in the app bundle.
Update June 2012
I've got a small example project on GitHub called PromNight which demonstrates using an Xcode Workspace with an iPad project and a OS X project to preload the data for Core Data. This uses an object model that is shared between the the two applications which helps to keep changes in sync when preloading.
Core Data uses a backing store, which is essentially a sqlite database (or, on Mac OS, optionally an XML file). You should simply add that file to your app's bundle and ship it with the app. As far as getting the data into the database, here's what I would do:
Write some code to import the data from whatever format you have it in.
Run that code.
Copy the sqlite file off of the device or from the simulator.
Add the newly created sqlite file to your project in Xcode.
I wouldn't hand-create the sqlite file, since Core Data does some "voodoo" behind the scenes and messing with the sqlite can break things. Also, I've seen developers use multiple targets. for the import. This way, they can write the code in a compiler conditional and then not have to worry as much about project maintenance. For example:
#ifdef kImportTarget
//run core data import
#else
// run the Core Data stack setup from an existing file
#endif
The Core Data database is just a SQLite database file. You can deliver it in your main bundle and then copy it to your documents folder before associating it with your persistent store coordinator.
I'm looking for a good way to manage many image files in my app.
When the number of images to maintain gets large, it seems vital to have a directory structure to hold them.(to organize images and to support duplicate image names)
Since normal way of storing images in documents directory(by adding images to xcode's resource folder) doesn't seem to support directory structure,
I probably need to use something called bundle.
Here are questions.
It's not clear to me what's the difference between "documents
directory" and "bundle". Are they
just names to specify directory path
inside an iphone application? Since
documents directory doesn't support
directory structure, I guess it's not
a regular file path in iOS? (I'm
looking for a definition or overview
description on those two terms enough
to help answering the following
questions)
How do I create a tree structure directory to store resources?
How do I add files to the created directory?
What is the step (probably in xcode) to add new files to the
directory as project grows? note:
question 3 deals with initial set up,
4 deals with update.
What happens to files under documents directory and bundle when
user updates the app? Since many
applications store user data
somewhere, there must be a way of
updating an app without wiping out the
saved user data. ie. How does
"documents directory" and "bundle"
behave in update situation?
So called "resource bundle" refers to the "bundle" used in above
questions?
Thank you.
Your app is a "bundle". It's represented by an NSBundle object. On iOS, this is the only bundle you are allowed to use; you can't create another bundle and import it into your app.
However, you can add a subdirectory to your app's bundle. In Xcode 4, select your project in the navigator and click on the Build Phases tab. Add a new build phase (bottom right), Copy Files. Move it up just below Copy Bundle Resources, and rename it something meaningful ("copy interface images", or something). You'll notice you've got a Subpath field there - that's your directory in your bundle. Drag the files you want in that subdirectory on to this build phase, and then you can access them through the normal methods in NSBundle, UIImage, NSData and so on.
Wish it was easier? Me too.
The Xcode templates for the creation of core data apps start a new blank sqlite file when the app is started the first time. But suppose I have a database already created that I need to include in the bundle, so, when the app starts the first time it already starts with a populated database.
How should I proceed. Ok, I know that I cannot write the database in the bundle, so I have to copy it to the document's directory. I see this is where the sqlite database created by the app itself is already on. So, that's it? I just overwrite the original file with the one in the bundle at the end of my RootViewController's viewDidLoad method?
If this is the way to go, then I need to build a control method that does that just the first time, right?
It must be a simpler way...
Any ideas?
thanks
You're on the right track with copying the .sqlite file from the application bundle to the documents directory. I used the approach outlined very thoroughly in this blog post by Jeff LaMarche. It deals specifically with providing staring data to an iPhone application, and it worked like a charm in my app.
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.
I'm working on a Core Data app (for iPhone 3.0, though I don't think that really makes a difference here) and it will need to ship with a "starter" database filled with data. With SQLite, I would just have the App copy the populated database from the bundle into the App's documents directory on first launch and then load that database - all the information would come along with it and we'd be ready to go. But with Core Data, I'm not really sure if I can just save the Persistent store to the App bundle and copy it before having Core Data start doing its thing. Will this cause any problems? There is quite a bit of initial data, so I don't want to package it in another format and have to parse through it.
Yes, you can copy over a pre-populated persistent store.
I created a Mac app that populates a store. It is copied into my bundle and at start, copied to the Docs directory. This works fine. I am told the Core Data Books example was developed the same way.
Please note this doesn't mean you can just copy over any old SQLite file. It has to be a Core Data persistent store, though I think you understand that based on your question.
Actually there is a trick: you must name the file you are going to copy over with an extension other than ".sqlite", ".bin" will do. Otherwise Xcode will change the contents of the file when it copies it into the app during the build phase and it won't load.