Open Radar

 
Summary:
If you read from the -[UIViewController topLayoutGuide] property before everything is fully laid out, something causes the contentSize of the controller's view to be set to {0,0}.  This then prevents you from being able to scroll properly - in the attached example, you can drag the tableview up, but it springs back into place without letting you see what's below the screen

Steps to Reproduce:
1 - create a UITableViewController in a UINavigationController (the one in the Master-Detail sample code will do)
2 - read from self.topLayoutGuide in awakeFromNib (or viewWillAppear, or viewWillLayoutSubviews, or...)


Expected Results:
Crazy content sizes like {0,0} should not be applied to the scroll view.

Actual Results:
Crazy content sizes like {0,0} are applied to the scroll view.

Version:
iOS 7.0.2

----------------


This is a variant of the Master-Detail sample app that demonstrates the problem : 



@implementation ABMasterViewController

- (void)awakeFromNib
{
    for(int i=0; i<20; i++) {
        [self insertNewObject:nil];
    }
    
    (void)self.topLayoutGuide;
    
    [super awakeFromNib];
}


- (void)insertNewObject:(id)sender
{
    if (!_objects) {
        _objects = [[NSMutableArray alloc] init];
    }
    [_objects insertObject:[NSDate date] atIndex:0];
    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
    [self.tableView insertRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}

#pragma mark - Table View

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _objects.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];

    NSDate *object = _objects[indexPath.row];
    cell.textLabel.text = [object description];
    return cell;
}

@end