Ray Ryan Zach Klippenstein Hello Square Workflow 

Nav logic sprawl Tragedy of convenient presenters 

CartScreen ChargeScreen TipScreen SignatureScreen ReceiptScreen 

class ChargeScreen { fun onCardSwiped(card: Card) { doStuffWithCard(card) if (tippingEnabled) goTo(TipScreen) else if (signatureRequired) goTo(SignatureScreen) else if (!skipReceipts) goTo(ReceiptScreen) else popTo(CartScreen) } } class TipScreen { fun onTip(tip: Money) { doStuffWithTip(tip) if (signatureRequired) goTo(SignatureScreen) else if (!skipReceipts) goTo(ReceiptScreen) else popTo(CartScreen) } } 

class ChargeScreen { fun onCardSwiped(card: Card) { doStuffWithCard(card) if (tippingEnabled) goTo(TipScreen) else if (signatureRequired) goTo(SignatureScreen) else if (!skipReceipts) goTo(ReceiptScreen) else popTo(CartScreen) } } class TipScreen { fun onTip(tip: Money) { doStuffWithTip(tip) if (signatureRequired) goTo(SignatureScreen) else if (!skipReceipts) goTo(ReceiptScreen) else popTo(CartScreen) } } 

CartScreen ChargeScreen TipScreen SignatureScreen ReceiptScreen 

class CheckoutWorkflow { } CartScreen ChargeScreen TipScreen SignatureScreen ReceiptScreen onCard / tipping onCard onTip onCard / skipSig onTip / skipSig onSig onSig / skipReceipt onReceipt 

Those who do not know React are condemned to reinvent it poorly. 

Workflow moving parts 

Workflow 

class NewGameScreen( val onStart: (String, String) -> Unit ) Rendering Workflow 

class NewGameScreen( val onStart: (String, String) -> Unit ) class NewGameRunner( view: View ) : LayoutRunner { val player1 = view.findById() // etc. fun showRendering(r: NewGameScreen) { playButton.setOnClickHandler { r.onStart(player1.text, player2.text) } } } LayoutRunner Workflow Rendering 

class NewGameScreen( val onStart: (String, String) -> Unit ) class NewGameRunner( view: View ) : LayoutRunner { val player1 = view.findById() // etc. fun showRendering(r: NewGameScreen) { playButton.setOnClickHandler { r.onStart(player1.text, player2.text) } } } LayoutRunner Workflow Rendering 

Let’s code! https://github.com/square/workflow/tree/zachklipp+ray/todo-android-livecode 

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