Tweet
Tweet

Slide 1

Slide 1 text

RETHINKING IOS APP ARCHITECTURE USING A ONE WAY DATA FLOW kat hawthorne, software engineer @square #hearandnow | @khhawthorne

Slide 2

Slide 2 text

#hearandnow | @khhawthorne

Slide 3

Slide 3 text

VIEW CONTROLLERS OUT OF CONTROL SHARED DATA CAUSES HARD TO DISCOVER BUGS CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST COMMON PROBLEMS IN IOS APPLICATIONS #hearandnow | @khhawthorne

Slide 4

Slide 4 text

VIEW CONTROLLERS HAVE TOO MUCH RESPONSIBILITY SHARED DATA CAUSES HARD TO DISCOVER BUGS CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST #hearandnow | @khhawthorne

Slide 5

Slide 5 text

YOUR CART IS EMPTY CART ADD ITEMS TO CHECKOUT #hearandnow | @khhawthorne

Slide 6

Slide 6 text

SHIRT $20 CALCULATE TOTAL CART #hearandnow | @khhawthorne

Slide 7

Slide 7 text

SKU ‘1234’ NOT FOUND CHECKOUT SHIRT $20 CALCULATE TOTAL CART #hearandnow | @khhawthorne

Slide 8

Slide 8 text

SHIRT $20 CHECKOUT 1 ITEM FOR $21 TAX $1 TOTAL $21 CART #hearandnow | @khhawthorne

Slide 9

Slide 9 text

SHIRT $20 CHECKOUT 1 ITEM FOR $21 TAX $1 TOTAL $21 [JIRA] (LST-99) CHECKOUT BUTTON COLOR DOES NOT UPDATE CART #hearandnow | @khhawthorne

Slide 10

Slide 10 text

VIEW CONTROLLERS HAVE TOO MUCH RESPONSIBILITY SHARED DATA CAUSES HARD TO DISCOVER BUGS CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST #hearandnow | @khhawthorne

Slide 11

Slide 11 text

SHIRT $20 CART CALCULATE TOTAL HAT $20 X #hearandnow | @khhawthorne

Slide 12

Slide 12 text

SHIRT $20 CART CALCULATE TOTAL HAT $20 X [JIRA] (LST-100) APP CRASHES WHEN CALCULATING TOTAL AND DELETING ITEM SIMULTANEOUSLY* #hearandnow | @khhawthorne

Slide 13

Slide 13 text

VIEW CONTROLLERS HAVE TOO MUCH RESPONSIBILITY SHARED DATA CAUSES HARD TO DISCOVER BUGS CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST #hearandnow | @khhawthorne

Slide 14

Slide 14 text

EMPTY CART CART WITH ITEMS VIEW CONTROLLER TESTS #hearandnow | @khhawthorne

Slide 15

Slide 15 text

EMPTY CART CART WITH ITEMS ERROR STATE SUCCESS STATE VIEW CONTROLLER TESTS #hearandnow | @khhawthorne

Slide 16

Slide 16 text

EMPTY CART CART WITH ITEMS ERROR STATE SUCCESS STATE ERROR STATE SUCCESS STATE VIEW CONTROLLER TESTS #hearandnow | @khhawthorne

Slide 17

Slide 17 text

EMPTY CART CART WITH ITEMS ERROR STATE SUCCESS STATE ERROR STATE SUCCESS STATE AND SO ON… VIEW CONTROLLER TESTS #hearandnow | @khhawthorne

Slide 18

Slide 18 text

ONE WAY FLOW OF DATA: THE CYCLE RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT #hearandnow | @khhawthorne

Slide 19

Slide 19 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT RENDERER #hearandnow | @khhawthorne

Slide 20

Slide 20 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT CONTEXT #hearandnow | @khhawthorne

Slide 21

Slide 21 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT PRESENTER #hearandnow | @khhawthorne

Slide 22

Slide 22 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW MODEL #hearandnow | @khhawthorne

Slide 23

Slide 23 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW CONTROLLER #hearandnow | @khhawthorne

Slide 24

Slide 24 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW #hearandnow | @khhawthorne

Slide 25

Slide 25 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT SERVICE #hearandnow | @khhawthorne

Slide 26

Slide 26 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT REPOSITORY #hearandnow | @khhawthorne

Slide 27

Slide 27 text

ONE WAY FLOW OF DATA: PUTTING IT TOGETHER RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT #hearandnow | @khhawthorne

Slide 28

Slide 28 text

AN EXAMPLE: ADDING AN ITEM TO THE CART #hearandnow | @khhawthorne

Slide 29

Slide 29 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT RENDERER class Renderer { func render() { let cartViewModel = CartPresenter.present( accountService: context.accountService, cartService: context.cartService, errorService: context.errorService, itemService: context.itemService ) cartViewController.update(cartViewModel) } } #hearandnow | @khhawthorne

Slide 30

Slide 30 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT CONTEXT class AppContext { private(set) lazy var cartService: CartService = CartService( cartState: self.cartState, catalogService: self.catalogService, accountService: self.accountService, render: self.render ) } #hearandnow | @khhawthorne

Slide 31

Slide 31 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT PRESENTER final class CartPresenter { class func present( accountService: AccountService, cartService: CartService, errorService: ErrorService, itemService: ItemService ) -> CartViewModel? {…} } #hearandnow | @khhawthorne

Slide 32

Slide 32 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW MODEL struct CartViewModel { let preSubtotalLineItems: [LineItem] let emptyCartMessage: String? let displayTotal: String? … } #hearandnow | @khhawthorne

Slide 33

Slide 33 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW CONTROLLER final class CartViewController : UIViewController { private(set) cartView: CartView = CartView() func update(viewModel: CartViewModel?){ cartView.emptyCartMessage = viewModel.emptyCartMessage cartView.displayTotalLabel = viewModel.displayTotal … } } #hearandnow | @khhawthorne

Slide 34

Slide 34 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT VIEW final class CartView : UIView { let emptyCartMessage: UILabel let displayTotalLabel: UILabel … } #hearandnow | @khhawthorne

Slide 35

Slide 35 text

RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT SERVICE class CartService { func addSKU(sku: String) { let item = catalog.getItem(sku: SKU) let cart = self.cart.mutableCopy() cart.mutableLineItems.addItemization(item) self.cart = cart.copy() render() } } #hearandnow | @khhawthorne

Slide 36

Slide 36 text

ONE WAY FLOW OF DATA: PUTTING IT TOGETHER RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT #hearandnow | @khhawthorne

Slide 37

Slide 37 text

VIEW CONTROLLERS OUT OF CONTROL SHARED DATA CAUSES HARD TO DISCOVER BUGS CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST COMMON PROBLEMS IN IOS APPLICATIONS #hearandnow | @khhawthorne

Slide 38

Slide 38 text

MULTI-LAYERED ARCHITECTURE SINGLE RESPONSIBILITY PRINCIPLE VIEW CONTROLLERS HAVE TOO MUCH RESPONSIBILITY LESS CODE = LESS MENTAL OVERHEAD #hearandnow | @khhawthorne

Slide 39

Slide 39 text

MINIMAL STATE IN THE APP CLEAR DELINEATION OF WHAT CAN MODIFY STATE SHARED DATA CAUSES HARD TO DISCOVER BUGS ONE WAY FLOW OF DATA ELIMINATES UNEXPECTED BEHAVIOR #hearandnow | @khhawthorne

Slide 40

Slide 40 text

THIN APPLICATION LAYERS DEPENDENCY INJECTION RATHER THAN RELYING ON SHARED STATE CODE WITH TOO MUCH RESPONSIBILITY IS HARD TO TEST #hearandnow | @khhawthorne

Slide 41

Slide 41 text

ONE WAY FLOW OF DATA: PUTTING IT TOGETHER RENDERER PRESENTER VIEW CONTROLLER VIEW SERVICE REPOSITORY VIEW MODEL CONTEXT #hearandnow | @khhawthorne

Slide 42

Slide 42 text

kat hawthorne @khhawthorne kh@squareup.com #hearandnow | @khhawthorne