Question

I use the following code to write to the plist (assuming dict is already populated):

[dict writeToFile:[appDelegate dataFilePath] atomically:YES];

where in my App Delegate:

- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:kFilename];
}

And I read the plist from disk using this:

NSMutableDictionary *dict = [[NSMutableDictionary alloc] initWithContentsOfFile:[appDelegate dataFilePath]];

This worked when compiling my app for 4.2, but since I brought it down to 4.1 for distribution, it stopped working.

[dict writeToFile:[appDelegate dataFilePath] atomically:YES];

returns NO. What’s wrong here?

Answer 1

I would guess that some other change is resulting in an object of non-plist type being present in your dictionary. See what happens if you separate out the “generate plist” and “write plist” steps:

/* Generate plist. */
NSError *error = nil;
NSData *data = [NSPropertyListSerialization
                dataFromPropertyList:dict
                format:NSPropertyListBinaryFormat_v1_0
                options:0/*unused*/
                error:&error];
if (!data) {
    NSLog(@"%s: Failed to serialize data: %@", __func__, error);
    return;
}

/* Write data. */
NSString *path = [appDelegate dataFilePath];
BOOL ok = [data writeToFile:dataFilePath options:NSDataWritingAtomic error:&error];
if (!ok) {
    NSLog(@"%s: Failed to write atomically to path %@: %@", __func__, path, error);
}