Writing Data to Plist as a Hierarchy

Question

I am working on an app that contains several sets of lists. These will contain a lot of items which will in turn contain more items. I want to save and load this to/from a PList in the docs directory, but I am unsure of how to write data in the hierarchy that I am looking for. This is the hierarchy:

>Lists
>>List1
>>>Item1
>>>>Item1Details
>>>Item2
>>>>Item2Details
>>>etc.
>>List2
>>>Item1
>>>>Item1Details
>>etc.

I have tried using NSDictionary writeToFile, but I still do not know how to have such a hierarchy.

Please give me some pointers on how to read/write this kind of thing. I am completely new to this use of plists, so please bear with me.

Cheers,

HBhargava

Answer 1

Perhaps, this will help you.

NSArray *paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"data.plist"];

    NSString Item1=@"Name";
    NSString Item2=@"Age";
    NSString Item1Detail=@"Khalid";
    NSString Item2Detail=@"21";


        NSMutableDictionary *_list1 = [[NSMutableDictionary alloc] init];
        NSMutableDictionary *_list2 = [[NSMutableDictionary alloc] init];

        [_list1 setValue:Item1Detail forKey:Item1];
        [_list1 setValue:Item2Detail forKey:Item2];

        [_list2 setValue:Item1Detail forKey:Item1];
        [_list2 setValue:Item2Detail forKey:Item2];

        NSMutableArray *_lists = [[NSMutableArray alloc] init];
        [_lists addObject:_list1];
        [_lists addObject:_list2];

        [_list1 release]
        [_list2 release];

        [_lists writeToFile:path atomically:YES];

        [_lists release];

Answer 2

As far as i can see is you have arrays of objects, here is the code for writing an array to a plist file in doc directory

    //look at this code which creates path to plist in documents directory:
    NSArray *paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"data.plist"];
//    >Lists
//      >>List1
//          >>>Item1
//              >>>>Item1Details
//          >>>Item2
//              >>>>Item2Details
//          >>>etc.
//      >>List2
//          >>>Item1
//              >>>>Item1Details
//    >>etc.

    NSArray *list1Arry = [NSArray arrayWithObjects:@"item1Detail",@"item2Detail",@"item3Detail", nil];
    NSArray *list2Arry = [NSArray arrayWithObjects:@"item1Detail",@"item2Detail",@"item3Detail", nil];
    NSArray *list3Arry = [NSArray arrayWithObjects:@"item1Detail",@"item2Detail",@"item3Detail", nil];
    NSArray *lists = [NSArray arrayWithObjects:list1Arry,list2Arry,list3Arry, nil];
    [lists writeToFile: path atomically:YES];

Answer 3

You can construct a hierarchy like this by setting another NSDictionary as a value within the root one. So, this code...

NSMutableDictionary *root = [NSMutableDictionary dictionary];
NSMutableDictionary *child1 = [NSMutableDictionary dictionary];
NSMutableDictionary *child2 = [NSMutableDictionary dictionary];

[child1 setValue:@"leaf1" forKey:@"key1"];
[child1 setValue:@"leaf2" forKey:@"key2"];

[child2 setValue:@"leaf3" forKey:@"key3"];
[child2 setValue:@"leaf4" forKey:@"key4"];

[root setValue:child1 forKey:@"child1"];
[root setValue:child2 forKey:@"child2"];

... would produce a root object like this:

{
   child1: {
      key1: leaf1
      key2: leaf2
   }
   child2: {
      key3: leaf3
      ley4: leaf4
   }
}

The object types that can be encoded automatically in a plist are NSString, NSData, NSDate, NSNumber, NSArray, and NSDictionary (see API).