UITableView Dynamically Create Sections from NSArray

You should do something like:

NSString *filePath = [[NSBundle mainBundle] pathForResource:@"name_of_plist" ofType:@"plist"];
NSArray *personsFileArray = [NSArray arrayWithContentsOfFile:filePath];
// At this point what you have inside personsFileArray are NSDictionaries as defined in your plist file. You have a NSArray<NSDictionary*>.
NSMutableDictionary *indexedPersons = [[NSMutableDictionary alloc] init];
// I am assuming you have a class called Person
for each (NSDictionary *d in personsFileArray) {
   Person *p = [[Person alloc] initWithDictionary:d];
   NSString *firstLetter = [p.lastName substringToIndex:1];
   NSMutableArray *persons = indexedPersons[firstLetter];
   if (!persons) {
      persons = [[NSMutableArray alloc] init];
   }
   [persons addObject:p];
   [indexedPersons setObject:persons forKey:firstLetter];
}
// After this, you have a dictionary indexed by the first letter, and as key an array of persons. 
// Now you need to implement UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    NSString *firstLetter = [self.indexedPersons allKeys][section];
    return self.indexedPersons[firstLetter].count;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 
{
    return [self.indexedPersons allKeys].count;
}

And implement this methods for the section index titles;

- (nullable NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section;
- (nullable NSArray<NSString *> *)sectionIndexTitlesForTableView:(UITableView *)tableView;
- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index;

If you have any doubts, there are plenty of tutorials:

http://www.appcoda.com/ios-programming-index-list-uitableview/

Hope it helps!!