Matthew Clarkson

Matthew Clarkson is a marketing technologist and founder at Cemoh

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UIViewController Extension to create a global UIActivityIndicatorView

06 Jan 2016

You shouldn’t repeat code, so don’t!

One of the many things iOS developers need to do over and over again is to display a UIActivityIndicatorView in a UIViewController. However, most of the time this seems to be accomplished by adding a UIActivityIndicatorView to each controller, which does not adhere to the DRY principle.

Thankfully, using Swift extensions, it is very easy to create a global activity indicator.

Firstly create UIViewController extension with a publicly accessible computed Int property, to use as the activity indicator tag identifier.

You can change the number to anything or override it in an individual controller, just make sure no other view has the same tag!

extension UIViewController {

    var activityIndicatorTag: Int { return 999999 }
}

Now we create a method called startActivityIndicator that dynamically creates an activity indicator and adds it to a view controller’s view.

This implementation allows you to customize the style (default is .Gray) and the location (default is the view controller view.center) but you can easily modify this (e.g. To disable touches).

extension UIViewController {

    //Previous code


    func startActivityIndicator(
        style: UIActivityIndicatorViewStyle = .Gray,
        location: CGPoint? = nil) {

        //Set the position - defaults to `center` if no`location`

        //argument is provided

        let loc = location ?? self.view.center

        //Ensure the UI is updated from the main thread

        //in case this method is called from a closure

        dispatch_async(dispatch_get_main_queue(), {

            //Create the activity indicator

            let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: style)
            //Add the tag so we can find the view in order to remove it later

            activityIndicator.tag = self.activityIndicatorTag
            //Set the location

            activityIndicator.center = loc
            activityIndicator.hidesWhenStopped = true
            //Start animating and add the view

            activityIndicator.startAnimating()
            self.view.addSubview(activityIndicator)
        })
    }
}

Now we create a method called stopActivityIndicator to remove the activity indicator.

extension UIViewController {

    //Previous code


     func stopActivityIndicator() {

        //Again, we need to ensure the UI is updated from the main thread!

        dispatch_async(dispatch_get_main_queue(), {
            //Here we find the `UIActivityIndicatorView` and remove it from the view

            if let activityIndicator = self.view.subviews.filter(
            { $0.tag == self.activityIndicatorTag}).first as? UIActivityIndicatorView {
                activityIndicator.stopAnimating()
                activityIndicator.removeFromSuperview()
            }
        })
    }
}

And there you have it - a globally accessible activity indicator that you can now call from any view controller!

This and many other extensions intended to reduce code repetition are available in the [HISwiftExtensions] (https://github.com/hilenium/HISwiftExtensions)library

Happy coding! Matt

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