buttons.m

- (void) setupButtons {
    NSMutableArray *buttons = [@[] mutableCopy];
    for (NSUInteger i = 0; i < TCInviteSectionFacebook; i++) {
        TCInviteFriendsTabButton *button = [[TCInviteFriendsTabButton alloc] init];
        button.translatesAutoresizingMaskIntoConstraints = NO;
        button.viewModel = self.viewModel;
        button.section = i;
        [buttons addObject:button];
        [self.view addSubview:button];
    }
    self.buttons = [buttons copy];
}

- (void) updateViewConstraints {
    if (!self.mainViewConstraintsSetup) {
        for (UIView *button in self.buttons) {
            NSInteger indexOfObject = [self.buttons indexOfObject:button];
            if (indexOfObject == 0) {
                [button pinEdge:NSLayoutAttributeLeft toEdge:NSLayoutAttributeLeft ofItem:self.view];
            } else {
                UIView *previousButton = [self.buttons objectAtIndex:indexOfObject - 1];
                [button pinEdge:NSLayoutAttributeLeft toEdge:NSLayoutAttributeRight ofItem:previousButton];
                [button pinAttribute:NSLayoutAttributeWidth toSameAttributeOfItem:previousButton];
            }
            if (indexOfObject == TCInviteSectionFacebook - 1) {
                [button pinEdge:NSLayoutAttributeRight toEdge:NSLayoutAttributeRight ofItem:self.view];
            }
            [button pinEdge:NSLayoutAttributeTop toEdge:NSLayoutAttributeBottom ofItem:self.topLayoutGuide];
            [button constrainToHeight:60];
        }
        
        [self.selectedTabIndicator constrainToHeight:2];
        [self.selectedTabIndicator pinAttribute:NSLayoutAttributeWidth toSameAttributeOfItem:self.buttons[0]];
        [self.selectedTabIndicator pinEdge:NSLayoutAttributeBottom toEdge:NSLayoutAttributeBottom ofItem:self.buttons[0]];
        self.mainViewConstraintsSetup = YES;
    }
    if (!self.leftIndicatorConstraint) {
        self.leftIndicatorConstraint = [self.selectedTabIndicator pinEdge:NSLayoutAttributeLeft toEdge:NSLayoutAttributeLeft ofItem:self.buttons[self.viewModel.currentSection]];
    }
    
    if (!self.childViewControllerConstraintsSetup) {
        UIView *childView = self.currentViewController.view;
        [childView pinToSuperviewEdges:(JRTViewPinLeftEdge|JRTViewPinBottomEdge|JRTViewPinRightEdge) inset:0];
        [childView pinEdge:NSLayoutAttributeTop toEdge:NSLayoutAttributeBottom ofItem:self.buttons[0]];
        self.childViewControllerConstraintsSetup = YES;
    }
    
    [super updateViewConstraints];
}