StatefulViewController

A view controller subclass that presents placeholder views based on content, loading, error or empty states.

In a networked application a view controller typically has the following states that need to be communicated to the user:

• Loading: The content is currently loaded over the network.
• Content: The content is available and presented to the user.
• Empty: There is currently no content available to display.
• Error: An error occured whilst downloading content.

As trivial as this flow may sound, there are a lot of cases that result in a rather large decision tree.

StatefulViewController is a concrete implementation of this particular decision tree. (If you want to create your own modified version, you might be interested in the state machine that is used to show and hide views.)

Usage

Configure the loadingView, emptyView and errorView properties of your StatefulViewController subclass in viewDidLoad.

After that, simply tell the view controller if content is currently being loaded and it will take care of showing and hiding the correct loading, error and empty view for you.

func loadDeliciousWines() {
	startLoading()
	
	let url = NSURL(string: "http://example.com/api")
	let session = NSURLSession.sharedSession()
	let task = session.dataTaskWithURL(url) { (let data, let response, let error) in
		endLoading(error: error)
	}
	task.resume()
}

StatefulViewControllerDelegate

StatefulViewController calls the hasContent delegate method to check if there is any content to display. If you do not implement this protocol, StatefulViewController will always assume that there is content to display.

func hasContent() -> Bool {
	return countElements(datasourceArray) > 0
}

Optionally, you might also be interested to respond to an error even if content is already shown. In this case, use handleErrorWhenContentAvailable to manually present the error to the user.

func handleErrorWhenContentAvailable(error: NSError) {
	let alertController = UIAlertController(title: "Ooops", message: "Something went wrong.", preferredStyle: .Alert)
	alertController.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
	self.presentViewController(alertController, animated: true, completion: nil)
}

View State Machine

Note: The following section is only intended for those, who want to create a stateful controller that differs from the flow described above.

You can also use the underlying view state machine to create a similar implementation for your custom flow of showing/hiding views.

let stateMachine = ViewStateMachine(view: view)

// Add states
stateMachine["loading"] = loadingView
stateMachine["other"] = otherView

// Transition to state
stateMachine.transitionToState(.View("loading"), animated: true) {
	println("finished switching to loading view")
}

// Hide all views
stateMachine.transitionToState(.None, animated: true) {
	println("all views hidden now")
}

Installation

pod "StatefulViewController", "~> 0.1"

For now, just drag and drop the two classes in the Source folder into your project.

Tests

Open the Xcode project and press ⌘-U to run the tests.

Alternatively, all tests can be run in the terminal using xctool (once it is ready for Xcode 6).

xctool -scheme Tests -sdk iphonesimulator test

Todo

• Default loading, error, empty views
• Protocol on views that notifies them of removal and add
• Views can provide delays in order to tell the state machine to show/remove them only after a specific delay (e.g. for hide and show animations)

Contributing

• Create something awesome, make the code better, add some functionality, whatever (this is the hardest part).
• Fork it
• Create new branch to make your changes
• Commit all your changes to your branch
• Submit a pull request

Contact

Feel free to get in touch.

• Website: http://schuch.me
• Twitter: @schuchalexander