KatanaRouter Save

App Navigation routing for Katana

Project README

KatanaRouter: App Navigation routing for Katana 🌲

This library is still under development

KatanaRouter is a declarative, type-safe app navigation router for Katana. Katana's state structure should represent the whole app's state, including the navigation. The only way to change the navigation state should be through actions.

That's exactly what this library lets you to do:

let pushAction = AddNewDestination(destination: Destination(routableType: RandomViewController.self))

KatanaRouter takes care of everything for you: storing the state, providing you actions to change the state, and finding differences between the navigation states.

Here's a small article I wrote, explaining how I implemented the algorithm that runs it.

Inspired by ReSwift-Router.



  • iOS 8.4+ / macOS 10.10+

  • Xcode 8.0+

  • Swift 3.0+


You can install KatanaRouter via CocoaPods by adding this line to your podfile:

pod 'KatanaRouter'

And run pod install.


KatanaRouter is totally decoupled from any UI framework. Under the hood it's a tree of Destination structures. Each Destination can contain children Destination, one of which can be active (visible).

A Destination can route to anything, a UIViewController, or even an UIView.

For example:

• A UITabBarController with UINavigationController as tabs, every one of which can push UIViewControllers on top of each other. It's modelled into a tree in which the tab bar controller is the root

               +     +   +
   +-----------+     |   +------------+
   |                 |                |
   |                 +                |
   +                                  +
Tab One(active)    Tab Two         Tab Three

   +                  +                +
   |                  |                |
   |                  |                |
   |                  +                |
   +                                   +
ChildVc(active)     ChildVc          ChildVc

• You can as easily model a UIViewController destination which has children UIView destinations in a UIScrollView and declaratively change the UIView children with an action. It means that you can use KatanaRouter to route your child UIViews.


Destination is a structure which models a unique destination, identified by a unique instanceIdentifier, or by userIdentifier set by you to easily refer to it later. Please make sure that all userIdentifiers are unique.

routableType is the type of the Routable conforming class that will support all the navigation changes callbacks.

You can also pass contextData inside, to receive it and use it when it comes time to navigate.

State Storage

KatanaRouter takes care of storing the current navigation state for you. All you have to do is make your state to conform to RoutableState protocol.

struct MyState: State, RoutableState {
    var navigationState: NavigationState = NavigationState()

Changing State

KatanaRouter provides you with actions to change the current state. If you want to request a new state change action, that's missing, please create an issue on GitHub.

func didTapPush() {
    // RandomViewController conforms to `Routable` type
    let pushAction = AddNewDestination(destination: Destination(routableType: RandomViewController.self))

Reacting to state change

KatanaRouter has an algorithm that finds differences between states and informs you about them. This is where all the concrete UI actions happen e.g. presentViewController, pushViewController, addSubview.

All you have to do is conform to the Routable protocol in objects that control your app's navigation actions.

extension RandomViewController: Routable {

Routable has 4 methods that it can implement:

• Push - Singular push action happened. You're responsible to push/present/show the destination and return it's Routable

func push(destination: Destination, completionHandler: @escaping RoutableCompletion) -> Routable {
    switch(destination.routableType) {
    case is RandomViewController.Type:
        // Instantiate and push/present/show an instance of `RandomViewController`
        // Remember to always call the `completionHandler`
        // Return a `Routable` responsible for the pushed destination
        return randomViewController
    default: fatalError("Not supported")

• Pop - Singular pop happened. You're responsible to pop/dismiss/remove the destination

func pop(destination: Destination, completionHandler: @escaping RoutableCompletion) {
    switch(destination.routableType) {
    case is RandomViewController.Type:
        // pop/dismiss/remove `randomViewController`
    default: fatalError("Not supported")

• Change - A more complex action. At least two singular pop/push actions. It gives you a chance to replace the destinations in one smooth transition. You're responsible for popping and pushing, you also need to return Routable's for all the freshly pushed destinations.

public func change(destinationsToPop: [Destination], destinationsToPush: [Destination], completionHandler: @escaping RoutableCompletion) -> [Destination : Routable] {
    var createdRoutables: [Destination : Routable] = [:]
    for destinationToPush in destinationsToPush {
        switch destinationToPush.routableType {
        case is FirstChildView.Type:
            // Show/add first child
            // You need to return the `Routable` that's responsible for routing the `FirstChildView` instance
            createdRoutables[destinationToPush] = firstChildInstance
        case is SecondChildView.Type:
            // Show/add second child
            // You need to return the `Routable` that's responsible for routing the `SecondChildView` instance
            createdRoutables[destinationToPush] = secondChildInstance
        default: fatalError("Not supported")
    // Remember to always call the CompletionHandler when finished with the transition!
    return createdRoutables

• ChangeActiveDestination - Called when there's a new destination set to active. You're responsible of setting the active destination to visible.

public func changeActiveDestination(currentActiveDestination: Destination, completionHandler: @escaping RoutableCompletion) {
    switch currentActiveDestination.routableType {
    case is FirstChildView.Type:
        self.selectedIndex = 0
    case is SecondChildView.Type:
        self.selectedIndex = 1
    default: fatalError("Not supported")


Feel free to contribute in any way 👍

Demo App

You can find a simple (work in progress) demo app at KatanaRouterDemo.

Open Source Agenda is not affiliated with "KatanaRouter" Project. README Source: michalciurus/KatanaRouter
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5 years ago

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