Can UIView be copied?

Question

Simply using this way:

UIView* view2 = [view1 copy]; // view1 existed

This will cause simulator can not launch this app.

Try retain,

UIView* view2 = [view1 retain]; // view1 existed
// modify view2 frame etc

Any modifications to view2 will apply to view1, I understand that view2 share same memory with view1.

Why can't UIView be copied? What is the reason?

Solution 1

Your app probably crashes with something like:

 [UIView copyWithZone:]: unrecognized selector sent to instance 0x1c6280

The reason is that UIView does not implement the copying protocol, and therefore there is no copyWithZone selector in UIView.

Solution 2

this might work for you ... archive the view and then unarchive it right after. This should give you a deep copy of a view:

id copyOfView = 
[NSKeyedUnarchiver unarchiveObjectWithData:[NSKeyedArchiver archivedDataWithRootObject:originalView]];

Solution 3

You can make an UIView extension. In example swift snippet below, function copyView returns an AnyObject so you could copy any subclass of an UIView, ie UIImageView. If you want to copy only UIViews you can change the return type to UIView.

//MARK: - UIView Extensions

    extension UIView
    {
       func copyView<T: UIView>() -> T {
            return NSKeyedUnarchiver.unarchiveObject(with: NSKeyedArchiver.archivedData(withRootObject: self)) as! T
       }
    }

Example usage:

let sourceView = UIView()
let copiedView = sourceView.copyView()

Solution 4

for swift3.0.1:

extension UIView{
 func copyView() -> AnyObject{
    return NSKeyedUnarchiver.unarchiveObject(with: NSKeyedArchiver.archivedData(withRootObject: self))! as AnyObject
 }
}

Solution 5

UIView doesn't implement the NSCoping protocol, see the declaration in UIView.h:

@interface UIView : UIResponder <NSCoding, UIAppearance, UIAppearanceContainer, UIDynamicItem, UITraitEnvironment, UICoordinateSpace, UIFocusEnvironment>

So, if we want to have a copy like method, we need to implement the NSCoping protocol in a category or so.

View more solutions

Comments

[Satyam]

What should I do to implement the copy of UIView?

[Anonymous White]

So if you have a certain combination of UIView and want to use that several time you will need to subclass such UIView?

[Engin Kurutepe]

Yes, subclassing or category with class-level factory methods that return preconfigured instances of that view.

[Patrick Borkowicz]

That seems like a bit of a hack but works like a dream. ssj's answer below is basically a 'copy constructor' which is fine for small classes. You can maybe use the obj-c runtime to copy all the properties at once.. This is still easier ;)

[bluefloyd8]

this isn't answering the question.

[Ortwin Gentz]

This sounds to good to be true. In my case it throws an NSInvalidArgumentException (NSConcreteAttributedString initWithString:: nil value) for a UILabel in the subview tree.

[Ian Newson]

This works, but seems to be very slow for even trivial view trees.

[nalexn]

It works, but beware! It does not set values for @IBOutlets, all of them are nil after "copying"

[Iulian Onofrei]

This seems to ignore UIImageViews :(

[Sajjon]

Thanks, works great! ALSO please note that the copied view has no superview (parent), no constraints and no gesture recognizers (if the parent had any).

[Sajjon]

Thanks, works great! ALSO please note that the copied view has no superview (parent), no constraints and no gesture recognizers (if the parent had any).

[Nick Entin]

agree with @IanNewson, just tried 2 approaches. A method, which: 1. instantiates new view and configure it 2. instantiates new view, configures it and archive. If archivation happened already, just call unarchiveObjectsWithData on saved data. 1. result of instantiation of 200 views, where this one is a subview ~ 0.5 sec. 2. result of instantiation of 200 views, where this one is a subview ~ 0.8 sec. The view is only UIImageView with couple autoresizing masks. I would not recommend archiving/unarchiving for duplication of views...

[iamirzhan]

what if your label has other custom parameters like numberOfLines or tag? Will you set all properties?

[paulvs]

This throws a value for key (UIHighlighted) is not a boolean exception when using UIImageViews. You can use let copyView = aView.snapshotView(afterScreenUpdates: true) instead.