在ViewController中实例化UIImageView时如何设置其大小/框架和contentMode？

Question

I have a view controller for my app that instatiates previewView, capturedImage and CapturedImageView like so

class ViewController: UIViewController, AVCaptureFileOutputRecordingDelegate, UIGestureRecognizerDelegate {
    @IBOutlet weak var previewView: AVCamPreviewView!

    var capturedImage: UIImage!
    var capturedImageView: UIImageView!
}

previewView is on the main.storyboard but the capturedImage and CapturedImageView are not. I want capturedImageView to be the exact same size as the previewView so normally I would do something like let capturedImageView = UIImageView(frame: self.previewView.frame)

but I don't seem to be able to use that syntax outside of a function. Additionally I'm not sure if the previewView actually exists yet for me to be able to do this....

It complains Value of type 'NSObject -> () -> ViewController' has no member 'previewView'

so I think it doesn't

so maybe I could do it after in viewDidLoad? But again I don't think I can just use self.capturedImageView = UIImageView(frame: self.previewView.frame) seeing as when I tried it I got this long hairy error message (and the app froze):

function signature specialization <Arg[0] = Exploded, Arg[1] = Exploded> of Swift.(_fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.UInt) -> ()).(closure #2)

Any suggestions?

Answer 1

I'm not sure how clear it is what you are trying to do — in the code you have given, you haven't instantiated anything.

If you are trying to instantiate capturedImageView directly with its declaration in the view controller, and referencing another property in the same view controller, you will not be able to do that, since you can only reference self (ie the view controller) once it is fully instantiated, and all its properties must be fully initialised before that.

Therefore you should either instantiate capturedImageView without a frame (and therefore not referencing self ), and then set its frame later on (in viewDidLoad for example, or you could make capturedImageView into a lazy property (which can then reference self since it will only be instantiated after full instantiation of the view controller.

If you are making frames of views equal to one another, you would of course be better off using autolayout, but that is a separate issue.