IPhone–json deserialization of custom objects

[Update – 27-Jan-2012, Starting with iOS5 you can use built-in NSJSONSerialization class,  example here: http://www.raywenderlich.com/5492/working-with-json-in-ios-5] 

After last entry on serialization I still owe a snippet for deserialization.
Since that time my class grew up a bit and now its json string read from db is:

{"environment":

  {"fixedLongitude":"14.471223","name":"mobile","fixedLatitude":"50.135194",

    "plans":[

        {"tasks":[{"title":"baby cries","dur":"10","durUnit":"2","desc":""}],

          "title":"babysitter!","description":""},      

        {"tasks":[{"title":"this is it","dur":"10","durUnit":"2","desc":""}],

          "title":"cook!","description":"Sample plan description"}]}}

And here is a snippet to reversing it back into the object (with jsonString value provided above):

    // Getting a json string from db

    NSString *jsonString = [[NSString alloc] initWithUTF8String: (char*) sqlite3_column_text (dbps, 0)];

    NSLog(@"data from db: %@", jsonString);

    // Top level dictionary, only contains "environment" key

    NSDictionary *dictionary = [jsonString JSONValue];

    // Retrieve "environment" itself

    NSDictionary *env = [dictionary objectForKey:@"environment"];

    // From "environment" dictionary get plans array as a "plans" key

    NSArray *plansArr = [env objectForKey:@"plans"];

    // For simple "environment" attributes retrieval is simple

    _environment.fixedLatitude = [[env objectForKey:@"fixedLatitude"] doubleValue];

    _environment.fixedLongitude = [[env objectForKey:@"fixedLongitude"] doubleValue];

    // Now getting to traverse the "plans" array, logic of traversal down the tree is same as above

    for (int i=0; i < [plansArr count]; i++) {

        NSDictionary *planJ = [plansArr objectAtIndex:i];

        Plan *p = [[Plan alloc] initWithTitle: [planJ objectForKey:@"title"] 

                                 description: [planJ objectForKey:@"description"]];

        NSArray *tasksJ = [planJ objectForKey:@"tasks"];

        for (int j=0; j < [tasksJ count]; j++) {

            NSDictionary *taskJ = [tasksJ objectAtIndex:j];

            [p AddTaskWithTitle:[taskJ objectForKey:@"title"] 
                       duration:[[taskJ objectForKey:@"dur"] intValue] unit: [[taskJ objectForKey:@"durUnit"] intValue] 
                       link:[taskJ objectForKey:@"desc"]];

    }

        [[_environment plans] addObject:p];

        [p release];

    }

    [jsonString release];

This is it!