iphone - Pre-load core data database in iOS 5 with UIManagedDocument

Question

I'm trying to come up with a way that I can pre-load data into core data while using an UIManagedDocument. My attempt so far is to make the document in a "Loader" app using this code..

NSURL *url  = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory
                                                      inDomains:NSUserDomainMask] lastObject];
url = [url URLByAppendingPathComponent:@"Default Database"];
if(![[NSFileManager defaultManager] fileExistsAtPath:[self.document.fileURL path]]){
    [self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success){
        if(success)[self loadDataIntoDocument];
    }];
}

and then copy the persistentStore file from the 'documents' directory that is created in the simulator's directory to the resources section in Xcode for the main app that will be using the loaded database.

My problem is that I can't figure out how to copy that document from the app bundle and use it as a document successfully.

I've tried copying the document directory as-is from the app bundle and trying to access it as a document which gave the error that UIManagedDocument can only access a package of files. I've tried creating another fresh document in the main app and copying the persistentStore from the bundle over the one that is created in the document with the same error. And I've tried using UIManagedDocument's -(BOOL)loadFromContents:ofType:error: method .. I'm not even sure this is what I should be using.

Does anyone have an idea as to how this is normally done? Thanks!

Answer 1

I don't think you should mess around with the files and directories yourself in iOS.

You can, however, open the document directly from your bundle. For that, you simply have to copy the whole document directory you created in your Loader app into your final bundle. The structure should be rather simple, just two directories with the persistentStore file inside.

Afterwards, when you want to open your document, you need to take care of two things: you need to use the bundle directory as the base directory and you need to add a / at the end of the "file" name, so UIManagedDocument knows that the directory is the document. The code looks like this:

NSURL* url = [[NSBundle mainBundle] bundleURL];
url = [url URLByAppendingPathComponent:@"filename/"];
UIManagedDocument* doc = [[UIManagedDocument alloc] initWithFileURL:url];

Note that you cannot write to that file, as you are not allowed to write inside your application bundle. So if you want to have a writable document, you need to copy that document into your documents folder. You can do that easily by simply saving doc to a different location:

[doc saveToURL:newURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success){}]

One more thing: You have to make sure the folder structure is created in your app bundle. The easiest way to make this happen is to drag the whole folder into your project and then select "Create folder references for any added folders". For the "file" symbollist_en (which is actually a bundle/folder itself) it should look like this:

If you do not do this, the "contents" of the document will reside in your app bundle directly, which cannot be opened as a UIManagedDocument, as you found out.