//UITableView的tableHeaderView高度自适应

Ext-UITableView.swift

//UITableView的tableHeaderView高度自适应
extension UITableView {
    //set the tableHeaderView so that the required height can be determined, update the header's frame and set it again
    func setAndLayoutTableHeaderView(header: UIView) {
        self.tableHeaderView = header

        for view in header.subviews {
            guard let label = view as? UILabel where label.numberOfLines == 0 else { continue }
            label.preferredMaxLayoutWidth = CGRectGetWidth(label.frame)
        }

        header.setNeedsLayout()
        header.layoutIfNeeded()
        var frame = header.frame

        let size = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize)
        frame.size = size

        header.frame = frame
        self.tableHeaderView = header
    }

    func sizeHeaderToFit(preferredWidth: CGFloat) {
        guard let headerView = self.tableHeaderView else {
            return
        }

        headerView.translatesAutoresizingMaskIntoConstraints = false
        let layout = NSLayoutConstraint(
                item: headerView,
                attribute: .Width,
                relatedBy: .Equal,
                toItem: nil,
                attribute:
                .NotAnAttribute,
                multiplier: 1,
                constant: preferredWidth)

        headerView.addConstraint(layout)

        let height = headerView.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
        headerView.frame = CGRectMake(0, 0, preferredWidth, height)

        headerView.removeConstraint(layout)
        headerView.translatesAutoresizingMaskIntoConstraints = true

        self.tableHeaderView = headerView
    }

}