So I'm laying out these components on the screen.

I add a UIView with an image, followed by a button.

I'm using autolayout, and set the button to be below the image, but it is aligning agains the top of the view.

Here's a code snippet:

let image = RexWalkingSilhouette(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: 200))
let button = MyButton("Start")

view.addSubview(image)
view.addSubview(button)
button.translatesAutoresizingMaskIntoConstraints = false
image.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([
    ...

    image.topAnchor.constraint(equalTo: subtitle.bottomAnchor, constant: 20),
    image.centerXAnchor.constraint(equalTo: subtitle.centerXAnchor),
    image.widthAnchor.constraint(equalTo: subtitle.widthAnchor),

    button.topAnchor.constraint(equalTo: image.bottomAnchor),
    button.centerXAnchor.constraint(equalTo: image.centerXAnchor),
    button.widthAnchor.constraint(equalToConstant: 100),
])

An here's an image (showing the views' bounds for clarity).

So what's wrong with my code. Why doesn't it align with the bottom anchor?

I am not sure but I would remove the manual frame setting from the image and use AutoLayout for it as well.

Doesn't seem to be the case. I just tested it.

And what about image.bottomAnchor.constraint(equalTo: button.topAnchor), ? (I reversed the items)

That puts the button above the image (also tested).

Yeah that was my suggestion but you said you tried that before ;)