无法从IOS中的plist文件中读取字典数据

Question

I have PropertyList.plist file in the "Supporting Files" folder. I have made a dictionary in it. The plist file is:

MY ViewController.m file code is

   @implementation GroupedInexedViewController
{
    NSDictionary *names;
    NSArray *keys;
}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *path = [[NSBundle mainBundle] pathForResource:@"PropertyList"
                                                     ofType:@"plist"];
    NSDictionary *dict = [[NSDictionary alloc]
                          initWithContentsOfFile:path];
    names = dict;
    [dict release];
    NSArray *array = [[names allKeys] sortedArrayUsingSelector:
                      @selector(compare:)];
    keys = array;
}

-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return [keys count];
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSString *key = [keys objectAtIndex:section];
    NSArray *nameSection = [names objectForKey:key];
    return [nameSection count];
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSUInteger section = [indexPath section];
    NSUInteger row = [indexPath row];

    NSString *key  = [keys objectAtIndex:section];
    NSArray *nameSection = [names objectForKey:key];
    static NSString *SectionsTableIdentifier = @"SectionsTableIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:SectionsTableIdentifier];
    if(cell == nil)
    {
        cell = [[[UITableViewCell alloc]
                 initWithStyle:UITableViewCellStyleDefault reuseIdentifier:SectionsTableIdentifier] autorelease];
    }
    cell.textLabel.text = [nameSection objectAtIndex:row];
    return cell;
}

-(NSString *) tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    NSString *key = [keys objectAtIndex:section];
    return key;
}

Unfortunately the "keys" array doesnt contain any element. Because I made an alert with its count value which is "keys.count" and it was zero. and also the "names" count was also zero. The path variable on vieDidLoad method shows the correct path. but it cant read from the dictionary of the plist file's.

Edit: I used nslog and it shows that in "viewDidLoad" method "names" is able to load the dictionary . but "keys" array is unable to load it.

Answer 1

What @EugeneK said worked but got sigabrt in "cellForRowAtIndexPath" method on the line

cell.textLabel.text = [nameSection objectAtIndex:row];

the error message is

"Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary objectAtIndex:]: unrecognized selector sent to instance 0x6832440".

The problem was nameSection variable was appearing as a NSDictionary type object which doesn't support objectAtIndex method.

So what I did I know is not a very good way to do it. I am sure there is some other way. I changed the 'viewDidLoad' method to this,

 - (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *path = [[NSBundle mainBundle] pathForResource:@"PropertyList"
                                                     ofType:@"plist"];
    names = [[NSDictionary alloc]
             initWithContentsOfFile:path];
    keys = [names allKeys];
    NSString *key = [keys objectAtIndex:0];
    names = [names objectForKey:key];
    keys = [[[names allKeys] sortedArrayUsingSelector:@selector(compare:)] retain];
    NSLog(@"keys = %@  names = %@",keys,names);
}

It works! Any idea how to do it better will be appreciated though.

Answer 2

Martin R is right. Please see comments in your code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *path = [[NSBundle mainBundle] pathForResource:@"PropertyList"
                                                     ofType:@"plist"];
    NSDictionary *dict = [[NSDictionary alloc]
                          initWithContentsOfFile:path]; //retainCount of dict is 1
    names = dict; // you made weak reference to dict
    [dict release]; // retainCount is 0 - dict is being dealloced
    NSArray *array = [[names allKeys] sortedArrayUsingSelector:
                      @selector(compare:)]; // you try to get data from dealloced object
    keys = array;
}

Try to do the following:

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *path = [[NSBundle mainBundle] pathForResource:@"PropertyList"
                                                     ofType:@"plist"];
    names = [[NSDictionary alloc]
             initWithContentsOfFile:path];

    keys = [[[names allKeys] sortedArrayUsingSelector:
            @selector(compare:)] retain];
}

And do not forgot to release names and keys in your view controller dealloc .