UIStackView not displaying - swift

Question

In my viewController viewDidLoad method I have:
let stackView = UIStackView()
stackView.axis = .Vertical
self.view.addSubview(stackView)
for _ in 1..<100{
let vw = UIButton(type: .System)
vw.setTitle("Button", forState: .Normal)
stackView.addArrangedSubview(vw)
}
but when I compile I only get a totally white screen.
What am I doing wrong?

Answer 1

You're adding the stack view to the parent view, but you're not telling the parent view how to lay the stack view out. If you're using constraint based layout, you need to pin the stack view to some of the edges of the parent view:
view.addConstraint(NSLayoutConstraint(item: stackView, Attribute: .Top, relatedBy: .Equal, toItem: self.view, attribute: .Top, multiplier: 1.0, constant: 0.0)
view.addConstraint(NSLayoutConstraint(item: stackView, Attribute: .Leading, relatedBy: .Equal, toItem: self.view, attribute: .Leading, multiplier: 1.0, constant: 0.0)
view.addConstraint(NSLayoutConstraint(item: stackView, Attribute: .Trailing, relatedBy: .Equal, toItem: self.view, attribute: .Trailing, multiplier: 1.0, constant: 0.0)
This will pin the stack view to the top, leading and trailing edges of the view.
The other approach would be to use Interface Builder to set up the constraints, as they are pretty verbose to manage in code.

Answer 2

You have add constraints or set frame for your stack view. Please check modified code below :
let stackView = UIStackView()
stackView.axis = .Vertical
stackView.distribution = .FillEqually
for i in 1..<100{
let vw = UIButton(type: .System)
vw.setTitle("Button\(i)", forState: .Normal)
stackView.addArrangedSubview(vw)
}
self.view.addSubview(stackView)
stackView.frame = self.view.bounds