UIStackView's own intrinsicContentSize

As of iOS 9.1, UIStackView doesn't implement intrinsicContentSize:

import UIKit
import ObjectiveC

let stackViewMethod = class_getInstanceMethod(UIStackView.self, "intrinsicContentSize")
let viewMethod = class_getInstanceMethod(UIView.self, "intrinsicContentSize")
print(stackViewMethod == viewMethod)

Output:

true

You could make a subclass of UIStackView and implement it yourself if you really need it. You shouldn't need to, though. If UIStackView is allowed (by the constraints on it) to choose its own size, it does so based on its arranged subviews' intrinsic content size (or by other constraints you've set on the sizes of its arranged subviews).