Programmatic UIView with subview not rendering in correct position - ios

Question

I'm trying to render a view that has a subview in it. However, the subview renders in the incorrect y-position.
ViewController is the parent view.
ViewController2 is a subview of ViewController and has it's own subview (let's call it X). X is being rendered in the incorrect y-position, even though ViewController2 and X have the same y value for their frames.
Edit:
I should note, X should be appear in the same position within ViewController2. Or at least, that's the intention.
See code below:
ViewController.swift
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
var y: CGFloat = 10
for vc in getVcs() {
self.view.addSubview(vc.render(x: 10, y: y))
y += 75
}
super.viewDidLoad()
}
func getVcs() -> [ViewController2] {
return [
ViewController2(),
ViewController2(),
ViewController2()
]
}
}
ViewController2.swift
import UIKit
class ViewController2: UIViewController {
func render(x: CGFloat, y: CGFloat) -> UIView {
let viewFrame = CGRect(x: x, y: y, width: 300, height: 50)
let xview = UIView(frame: viewFrame)
let subViewFrame = CGRect(x: x, y: y, width: 200, height: 25) // X
let subView = UIView(frame: subViewFrame)
subView.layer.borderColor = UIColor.green.cgColor
subView.layer.borderWidth = 1
xview.addSubview(subView)
xview.layer.borderColor = UIColor.red.cgColor
xview.layer.borderWidth = 1
return xview
}
}
How they appear at runtime:
(Green border represents X and the red border represents ViewController2.)
Any help would be appreciated!

Answer 1

A view defines its own frame in relation to its parent view.
In ViewController2, the subview you instantiated based on y parameter is getting added in relation to its parent view (the red box).
The solution is to change y value in relation to parent frame on your subview frame
let subViewFrame = CGRect(x: x, y: y, width: 200, height: 25) // X
Also to get a clear idea what's happening, try adding another ViewController2() in getVCs() and it will look like this.
As you can see, your code is not misplacing the second view as it looks like from your screen shot. It's placing the green box further and further in relation to its parent frame. Third frame was just a lucky hit. Hope this helps =)

Answer 2

Frames are specified in their SUPERVIEW'S COORDINATES. Your bounds are in the current view's coordinates. Therefore ViewController2's frame needs to be expressed as relative to ViewController 's frame, not relative to the window.