Reload View Controller and programatically change UIImageView constraint

Question

I have a UIImageView which its height is affected by the aspect ratio of a photo that the user either takes or selects from their library. I am having trouble getting the UIImageView to resize appropriately (or at all) after the user selects a photo.

Code:

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        //let mediaType2 : UIImage = info[UIImagePickerControllerOriginalImage] as! UIImage
        let mediaType : CFString = info[UIImagePickerControllerMediaType] as! CFString

        if mediaType == kUTTypeMovie {
            let path = (info[UIImagePickerControllerMediaURL] as! NSURL).path
            if UIVideoAtPathIsCompatibleWithSavedPhotosAlbum(path!) {
                UISaveVideoAtPathToSavedPhotosAlbum(path!, self, "video:didFinishSavingWithError:contextInfo:", nil)
            }
        }
        else{
            let img : UIImage = info[UIImagePickerControllerOriginalImage] as! UIImage
            let screenSize: CGRect = UIScreen.mainScreen().bounds
            let multiplyNum = screenSize.width / img.size.width
            imageView.frame = CGRectMake(0, 0, screenSize.width, multiplyNum*img.size.height)
            imageView.image = img

        }

        self.dismissViewControllerAnimated(true, completion: {})

    }

The constraints are currently set up inside the storyboard but I want to programatically override imageView's constraint.

Answer 1

You should update the constraints of the UIImageView rather than setting the frame. Set a height constraint for the image view then create an IBOutlet for that constraint (control drag from the constraint into it's view controller), call it something like "imageViewHeightConstraint." Then in your code say something like:

imageViewHeightConstraint.constant = multiplyNum*img.size.height