How to programmatically scroll a tableview to the top, then run a block when it's done animating. #ReactiveCocoa

gistfile1.m

[[[RACObserve(self.tableView, contentOffset)
 filter:^BOOL(NSValue *contentOffset) {
     CGPoint point = [contentOffset CGPointValue];
     return point.y == 0.0f;
 }]
 take:1]
 subscribeCompleted:^{
     // This block gets executed when the tableview has scrolled to top
 }];

[self.tableView scrollRectToVisible:CGRectMake(0, 0, 1, 1) animated:YES];