1) Access the height in viewDidAppear lifecycle method

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    
        //access the view size here.
        
    }

2) Use Dispath Queue’s Main queue

      DispatchQueue.main.async {
        //access the size here..
      }

3) Call layout update methods before access the size as below

    func getSizeOFTheView() {
        self.setNeedsLayout()
        self.layoutIfNeeded()

        //now access the view size
    }

4) Override the viewDidLayoutSubViews method as below,

    override viewDidLayoutSubviews() {
        //access the size here...
    }

There are few other ways too but i believe above mentioned points would be more helpful. you can use them as per your requirements.

Happy coding 👍