Ios/swift/view

こんな感じで入れたものを

let height = NSLayoutConstraint(item: tabView,
           attribute: .Height,
           relatedBy: .Equal,
           toItem: nil,
           attribute: .Height,
           multiplier: 1.0,
           constant: option.tabHeight)
tabView.addConstraint(height)
view.addSubview(tabView)

こうやって取得できる

tabView = view.subviews.last
constraint = tabView.constraints.last
constraint.constant // height