Question

I have an iPhone application in which a number of domain objects are populated with user-entered data. In order to restore state after being interrupted, these objects implement the NSCoding protocol and are written to disk (the Documents directory) in the applicationWillTerminate message. Then, when the application is launched again, the bytes of data are loaded up and the domain objects are repopulated. Code to get the documents directory is as follows:

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

This worked great in the simulator but once I deployed the app to the iPhone it stopped working. The reason why is iPhone error code 513 – which apparently means “permission denied.” There is a note in the iPhone dev docs that explain a little bit more –

On the device, the returned path
(documentsDirectory) is similar to the
following:
/var/mobile/Applications/30B51836-D2DD-43AA-BCB4-9D4DADFED6A2/Documents

However, on the Simulator, the
returned path takes the following
form:

/Volumes/Stuff/Users/johnDoe/Library/Application
Support/iPhone
Simulator/User/Applications/118086A0-FAAF-4CD4-9A0F-CD5E8D287270/Documents

This is the exact behavior that I’m seeing. I’m not really sure how this relates to getting a permission denied error and what I can do to fix it. It does say below –

To read and write user preferences,
use the NSUserDefaults class or the
CFPreferences API. These interfaces
eliminate the need for you to
construct a path to the
Library/Preferences/ directory and
read and write preference files
directly. For more information on
using these interfaces, see “Adding
the Settings Bundle.”

If your application contains sound,
image, or other resources in the
application bundle, you should use the
NSBundle class or CFBundle opaque type
to load those resources. Bundles have
an inherent knowledge of where
resources live inside the application.
In addition, bundles are aware of the
user’s language preferences and are
able to choose localized resources
over default resources automatically.
For more information on bundles, see
“The Application Bundle.”

I don’t see how I can use the Application Bundle to load bytes of data though. Any help or examples?

Answer 1

Not sure how this works, but apparently using stringByAppendingPathComponent instead of stringByAppendingString for path creation fixed the problem.