如何读写NSArray到plist？

Question

I'm having several issues based around reading and writing an NSArray to and from a plist.

I have created a plist file in the 'Supporting Files' folder which I want to use to initialise the app data with upon the first load.

Here is what my plist looks like:

I then use this code to try load the plist into the app:

    NSError *error;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    filePath = [documentsDirectory stringByAppendingPathComponent:kDataFile];

    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:filePath])
    {
        NSString *bundle = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"plist"];
        [fileManager copyItemAtPath:bundle toPath:filePath error:&error];
    }

I then try to load the data from the plist file like so, however nothing seems to be displayed.

NSMutableDictionary *savedData = [[NSMutableDictionary alloc] initWithContentsOfFile:filePath];
NSMutableArray *myNSArray = [[savedData objectForKey:@"KEY_Level_1"] mutableCopy];
savedData = nil;

Sorry if this is a simple task, however I've been looking at lots of tutorials and trying to work out how to do this with no luck. I'm getting really frustrated now - I would have thought it should be a simple thing to do.

NOTE: My NSArray will contain a whole bunch of NSDictionaries.

Answer 1

1. You need to check the return value of copyItemAtPath:toPath:error: and at least log the error if the method returns false:

    if (![fileManager copyItemAtPath:bundle toPath:filePath error:&error]) { NSLog(@"error: copyItemAtPath:%@ toPath:%@ error:%@", bundle, filePath, error); return; } 

2. -[NSDictionary initWithContentsOfFile:] has no way to report errors, so if it's failing, you cannot easily figure out why. Try reading the file into an NSData and using -[NSPropertyListSerialization propertyListWithData:options:format:error:] to parse it:

    NSData *data = [NSData dataWithContentsOfFile:filePath options:0 error:&error]; if (!data) { NSLog(@"error: could not read %@: %@", filePath, error); return; } NSMutableDictionary *savedData = [NSPropertyListSerialization propertyListWithData:data options:NSPropertyListMutableContainers format:NULL error:&error]; if (!savedData) { NSLog(@"error: could not parse %@: %@", filePath, error); return; } NSMutableArray *myNSArray = [savedData objectForKey:@"KEY_Level_1"]; savedData = nil; if (!myNSArray) { NSLog(@"error: %@: object for KEY_Level_1 missing", filePath); return; } 

If you do this, you'll be able to more easily see why your data is not being loaded.

UPDATE

On further inspection, it looks like the top-level dictionary in your plist contains the key "Root". The value for "Root" is a dictionary containing the key "KEY_Level_1". So you need to do this:

NSMutableArray *myNSArray = [[savedData objectForKey:@"Root"] objectForKey:@"KEY_Level_1"];