UIViewController extension to add Previous, Next, and Done buttons to a group of UITextFields

UIViewController+InputAccessory.swift

extension UIViewController {
	func addInputAccessoryForTextFields(textFields: [UITextField], dismissable: Bool = true, previousNextable: Bool = false) {
		for (index, textField) in textFields.enumerate() {
			let toolbar: UIToolbar = UIToolbar()
			toolbar.sizeToFit()
			
			var items = [UIBarButtonItem]()
			if previousNextable {
				let previousButton = UIBarButtonItem(image: UIImage(named: "Backward Arrow"), style: .Plain, target: nil, action: nil)
				previousButton.width = 30
				if textField == textFields.first {
					previousButton.enabled = false
				} else {
					previousButton.target = textFields[index - 1]
					previousButton.action = #selector(UITextField.becomeFirstResponder)
				}
				
				let nextButton = UIBarButtonItem(image: UIImage(named: "Forward Arrow"), style: .Plain, target: nil, action: nil)
				nextButton.width = 30
				if textField == textFields.last {
					nextButton.enabled = false
				} else {
					nextButton.target = textFields[index + 1]
					nextButton.action = #selector(UITextField.becomeFirstResponder)
				}
				
				items.appendContentsOf([previousButton, nextButton])
			}
			
			let spacer = UIBarButtonItem(barButtonSystemItem: .FlexibleSpace, target: nil, action: nil)
			let doneButton = UIBarButtonItem(barButtonSystemItem: .Done, target: view, action: #selector(UIView.endEditing))
			items.appendContentsOf([spacer, doneButton])
			
			toolbar.setItems(items, animated: false)
			textField.inputAccessoryView = toolbar
		}
	}
}

//example
let field1 = UITextField()
let field2 = UITextField()
addInputAccessoryForTextFields([field1, field2], dismissable: true, previousNextable: true)