variable becomes nil in numberOfRowsInTableView after being set in another method - objective-c

Question

My class looks like this :
#interface ApplicantPickerController : AppPage <NSTableViewDataSource, NSTableViewDelegate>
{
School *school;
__weak IBOutlet NSTableView *tableView;
NSMutableArray *familyList;
__weak IBOutlet NSProgressIndicator *progressIndicator;
}
- (IBAction)alphabetButtonPressed:(id)sender;
#end
In the alphabetButtonPressed method, I'm fetching a json array from a webservice and assigning it to familyList. After doing this, I do [tableView reload];
When the control passes to the - (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView method, familyList becomes nil. Why is this happening and how can I fix it?
I'm using ARC for this project.
Cocoa/Objective-C newbie here. Any help would be much appreciated. Thank you!
Updated - Here is the implementation of the class :
#interface ApplicantPickerController ()
#end
#implementation ApplicantPickerController
- (IBAction)alphabetButtonPressed:(id)sender {
[progressIndicator startAnimation:self];
NSString * addy = [[NSString alloc] initWithFormat:#"%#.php?function=applicant_lookup&schoolID=%#&alpha=%#&currentYear=%#&format=json", BASE_URL_SCHOOL, school->recordID, [sender title], school->CurrentYear];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:addy]];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if(data) {
//NSString * resp = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSError *error = nil;
NSObject *json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
if([json isKindOfClass:[NSDictionary class]])
{
familyList = nil;
[tableView reloadData];
}
else if ([json isKindOfClass:[NSArray class]])
{
familyList = [[NSMutableArray alloc] init];
[familyList addObjectsFromArray:(NSArray*)json];
//[_familyList retain];
[tableView reloadData];
}
[progressIndicator stopAnimation:self];
}
}];
}
- (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView {
return [familyList count];
}
- (id)initWithMainView:(NSView *)_theView AndMainController:(NSViewController *)_theViewController AndNibName:(NSString *)nibName AndArgs:(NSArray *)_args
{
self = [super initWithMainView:_theView AndMainController:_theViewController AndNibName:nibName AndArgs:_args];
school = [args objectAtIndex:0];
return self;
}
#end

Answer 1

I don't know if I discovered a bug by apple, but following is how I solved this issue.
I was setting the NSTableView delegate and datasource in the UI builder (by right clicking and making the connections with the mouse). For some reason, if I set the delegate and dataSource in the code (specifically in the awakeFromNib method), the issue gets resolved.
- (void)awakeFromNib {
tableView.delegate = self;
tableView.dataSource = self;
}