Alternative for a table view cell’s content view’s layoutMarginsGuide that works on iOS 10.

PSPDFTableViewCell+LayoutMarginsGuide.m

@implementation PSPDFTableViewCell // UITableViewCell subclass

/**
 On iOS 10, constraints involving a UITableViewCell’s contentView’s layoutMarginsGuide are removed for some
 reason before the cell appears, which breaks the layout. This layout guide is a working alternative.
 */
- (UILayoutGuide *)pspdf_layoutMarginsGuide {
    if (@available(iOS 11.0, *)) {
        return self.contentView.layoutMarginsGuide;
    }

    // Constraints to layoutMarginsGuide disappear on iOS 10 for some reason.

    if (!_pspdf_layoutMarginsGuide) {
        let layoutGuide = [[UILayoutGuide alloc] init];
        [self.contentView addLayoutGuide:layoutGuide];

        self.layoutMarginsGuideLeadingConstraint = [layoutGuide.leadingAnchor constraintEqualToAnchor:self.contentView.leadingAnchor];
        self.layoutMarginsGuideTrailingConstraint = [self.contentView.trailingAnchor constraintEqualToAnchor:layoutGuide.trailingAnchor];
        self.layoutMarginsGuideTopConstraint = [layoutGuide.topAnchor constraintEqualToAnchor:self.contentView.topAnchor];
        self.layoutMarginsGuideBottomConstraint = [self.contentView.bottomAnchor constraintEqualToAnchor:layoutGuide.bottomAnchor];

        [NSLayoutConstraint activateConstraints:@[
            self.layoutMarginsGuideLeadingConstraint,
            self.layoutMarginsGuideTrailingConstraint,
            self.layoutMarginsGuideTopConstraint,
            self.layoutMarginsGuideBottomConstraint,
        ]];
        _pspdf_layoutMarginsGuide = layoutGuide;
    }
    return _pspdf_layoutMarginsGuide;
}

- (void)layoutMarginsDidChange {
    [super layoutMarginsDidChange];

    if (_pspdf_layoutMarginsGuide == nil) {
        // If it’s not loaded there’s nothing to do.
        return;
    }

    bet isRtL = self.pspdf_isRightToLeftLayoutDirection;
    let margins = self.layoutMargins;

    self.layoutMarginsGuideLeadingConstraint.constant = isRtL ? margins.right : margins.left;
    self.layoutMarginsGuideTrailingConstraint.constant = isRtL ? margins.left : margins.right;
    self.layoutMarginsGuideTopConstraint.constant = margins.top;
    self.layoutMarginsGuideBottomConstraint.constant = margins.bottom;
}

@end