What I learnt using the 
 Presenter Pattern

Know thy pattern Primer on MVC, MVP, MVVM

Know thy patterns View Controller Model user events modifies fire state change events MVC

Know thy patterns MVP View Presenter Model User interaction user events modifies fire state change events updates

View Presenter Model User interaction user events modifies fire state change events updates Know thy patterns MVP Passive

View Model User interaction Know thy patterns MVP user events modifies updates Supervising
 Controller Data Binding

View Model Know thy patterns MVVM Data Binding View Model update state fire state change (view queries VM again) (Presentation Model)

MVVM MVC MVP View Controller Model user events modifies state change events View Presenter Model User interaction user events modifies state change events updates View Model View Model modifies state changes Know thy patterns Data Binding

Evolve a Pattern "Architecture changes" are painful Introducing patterns is awesome

Evolve a Pattern class Customer {
 String dateOfBirth; String fullName; } "Bruce Lee" "1940-11-27" Don't add to the Model! Create a ViewModel class CustomerViewModel {
 Customer user;
 
 CustomerViewModel(Customer user) {
 this.user = user;
 }
 
 boolean canPurchaseAlcohol() {
 // return age() > 18;
 }
 
 String getInitials() {
 // return strip(user.fullName);
 }
 }

Don't use terms interchangeably ! ViewModel != Presenter

Don't use terms interchangeably Model Database structure or
 mirror of REST JSON Model decorates View Model

Don't use terms interchangeably Activities Fragments Views decorates Presenters Model decorates View Model ! Model

Where to put the Presenter? ¯\_(ϑ)_/¯

Where to put the Presenter? Activity Fragment Fragment ListView Adapter ViewHolder ViewHolder View ActivityPresenter? FragmentPresenter? ListViewPresenter? AdapterPresenter? ViewHolderPresenter? ViewPresenter?

Where to put the Presenter? Activity Fragment Fragment ListView Adapter ViewHolder ViewHolder View ActivityPresenter? FragmentPresenter? ListViewPresenter? AdapterPresenter? ViewHolderPresenter? ViewPresenter?

Death by Boilerplate :(

Use some form of DataBinding! Death by Boilerplate EventBus(es) So how does one combat the Boilerplate? Use some form of DataBinding! EventBus(es)

CheckoutActivity CheckoutActivityPresenter CheckoutAPresenterView Interface cause Java! CheckoutAdapter PaymentCardViewHolder AdapterPresenter PaymentCardVHPresenter AdapterPresenterView VHPresenterView implements new (View activity) { mView = activity; } CheckoutActivityPresenter AdapterPresenter new (View adapter) { mView = adapter; } mCheckoutActivityPresenter mAdapterPresenter Death by Boilerplate

CheckoutActivity CheckoutActivityPresenter CheckoutAPresenterView CheckoutAdapter PaymentCardViewHolder AdapterPresenter PaymentCardVHPresenter AdapterPresenterView VHPresenterView new (View activity) { mView = activity; } CheckoutActivityPresenter AdapterPresenter Button.onClick(event) new (View adapter) { mView = adapter; } mCheckoutActivityPresenter mAdapterPresenter launchPaymentActivity() Death by Boilerplate

CheckoutActivity CheckoutActivityPresenter CheckoutAPresenterView CheckoutAdapter PaymentCardViewHolder AdapterPresenter PaymentCardVHPresenter AdapterPresenterView VHPresenterView new (View activity) { mView = activity; } CheckoutActivityPresenter AdapterPresenter Button.onClick(event) new (View adapter) { mView = adapter; } mCheckoutActivityPresenter mAdapterPresenter launchPaymentActivity() OR ...... use an EventBus Death by Boilerplate

CheckoutActivity CheckoutActivityPresenter CheckoutAPresenterView CheckoutAdapter PaymentCardViewHolder AdapterPresenter PaymentCardVHPresenter Death by Boilerplate (Event Bus) AdapterPresenterView VHPresenterView new (View activity) { mView = activity; } Button.onClick(event) new (View adapter) { mView = adapter; } mCheckoutActivityPresenter mAdapterPresenter launchPaymentActivity() bus.post(event) @Subscribe

Compose Presenters ¯\_ + _/¯

Compose Presenters

Reinforce reasons for pattern

(Unit) Testing is faster and easier*

...But UI testing exists

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