Home Improvement: Architecture & Kotlin

Home Improvement:
Architecture & Kotlin
Jorge D. Ortiz-Fuentes
@jdortiz

#AdvArchMobile
A Canonical
Examples
Production

#AdvArchMobile
Agenda
★ Architecture
★ Kotlin
★ Recap

Persistance FW
View
Network
LocationFW
Presenter
Entity Gateway
Clean Architecture
Interactor
Entity

Dependency Inversion
Principle
High Level Low LevelAbstraction
Low Level

#AdvArchMobile
Respectful Criticism
about some
Opinionated
Decisions

#AdvArchMobile
Architecture Components
★ Awesome starting point
★ View Models (inner layer) depend on the
SDK:AndroidViewModel (outer layer)

#AdvArchMobile
Kotlin
★ Conciseness
★ Data Classes
★ Extensions
★ Property Delegation
★ Sealed Classes

#AdvArchMobile
Conciseness (code)
@Module public class ProgrammersListModule { 
private ProgrammersListActivity activity; 
 
public ProgrammersListModule(ProgrammersListActivity activity)
{ this.activity = activity; } 
 
@Provides ProgrammersListPresenter
provideProgrammersListPresenter(ShowProgrammersListUseCase useCase) { 
ProgrammersListPresenter presenter = new
ProgrammersListPresenter(useCase); 
useCase.setPresenter(presenter); 
presenter.setView(activity); 
return presenter; 
} 
 
@Provides ProgrammersListConnector provideProgrammersListConnector()
{ 
return new ProgrammersListConnector(activity); 
} 
}

#AdvArchMobile
@Module class ProgrammersListModule(private val activity: ProgrammersListActivity) { 
@Provides fun provideProgrammersListPresenter(useCase:
ShowProgrammersListUseCase): ProgrammersListPresenter = 
ProgrammersListPresenter(useCase = useCase).apply { 
useCase.presenter = this 
view = activity 
} 
 
@Provides fun provideProgrammersListConnector() = ProgrammersListConnector(view
= activity) 
}
Conciseness (code)
@Module public class ProgrammersListModule { 
private ProgrammersListActivity activity; 
 
public ProgrammersListModule(ProgrammersListActivity activity) { this.activity = activity; } 
 
@Provides ProgrammersListPresenter provideProgrammersListPresenter(ShowProgrammersListUseCase useCase) { 
ProgrammersListPresenter presenter = new ProgrammersListPresenter(useCase); 
useCase.setPresenter(presenter); 
presenter.setView(activity); 
return presenter; 
} 
 
@Provides ProgrammersListConnector provideProgrammersListConnector() { 
return new ProgrammersListConnector(activity); 
} 
}

#AdvArchMobile
@Module class ProgrammersListModule(private val
activity: ProgrammersListActivity) { 
@Provides fun
provideProgrammersListPresenter(useCase:
ShowProgrammersListUseCase): ProgrammersListPresenter = 
ProgrammersListPresenter(useCase =
useCase).apply { 
useCase.presenter = this 
view = activity 
} 
 
@Provides fun provideProgrammersListConnector() =
ProgrammersListConnector(view = activity) 
}
Conciseness (code)

#AdvArchMobile
Conciseness (test)
@Test public void
itemIsConfiguredWithNameOfFetchedProgrammer() { 
ProgrammersListItemView item =
Mockito.mock(ProgrammersListItemView.class); 
List<ProgrammerResponse> data = new
ArrayList<ProgrammerResponse>() {{ 
add(TestUtils.createMainProgrammerResponse()); 
add(TestUtils.createAltProgrammerResponse()); 
}}; 
ArgumentCaptor<String> captor =
ArgumentCaptor.forClass(String.class); 
sut.presentProgrammers(data); 
sut.configureItem(item, 1); 
verify(item).displayName(captor.capture()); 
assertEquals(TestData.programmerAltFullName,
captor.getValue()); 
}

#AdvArchMobile
@Test fun itemIsConfiguredWithNameOfFetchedProgrammer() { 
val item = mock<ProgrammersListItemView>() 
val data = listOf(TestData.createMainProgrammerResponse(), 
TestData.createAltProgrammerResponse()) 
sut.present(programmers = data) 
 
sut.configureItem(item, 1) 
 
argumentCaptor<String>().apply { 
verify(item).displayName(capture()) 
assertEquals(TestData.altFullName, lastValue) 
} 
}
Conciseness
@Test public void itemIsConfiguredWithNameOfFetchedProgrammer() { 
ProgrammersListItemView item = Mockito.mock(ProgrammersListItemView.class); 
List<ProgrammerResponse> data = new ArrayList<ProgrammerResponse>() {{ 
add(TestUtils.createMainProgrammerResponse()); 
add(TestUtils.createAltProgrammerResponse()); 
}}; 
ArgumentCaptor<String> captor = ArgumentCaptor.forClass(String.class); 
sut.presentProgrammers(data); 
sut.configureItem(item, 1); 
verify(item).displayName(captor.capture()); 
assertEquals(TestData.programmerAltFullName, captor.getValue()); 
}

#AdvArchMobile
@Test fun itemIsConfiguredWithNameOfFetchedProgrammer() { 
val item = mock<ProgrammersListItemView>() 
val data =
listOf(TestData.createMainProgrammerResponse(), 
TestData.createAltProgrammerResponse()) 
sut.present(programmers = data) 
 
sut.configureItem(item, 1) 
 
argumentCaptor<String>().apply { 
verify(item).displayName(capture()) 
assertEquals(TestData.altFullName, lastValue) 
} 
}
Conciseness

#AdvArchMobile
Entities
data class Programmer(
val firstName: String,
val lastName: String,
val emacs: Int, val caffeine: Int, 
val realProgrammerRating: Int,
val interviewDate: Date,
val favorite: Boolean) { 
val fullName: String 
get() = "$firstName $lastName" 
}

#AdvArchMobile
But
★ Not a value type
★ No defensive copy

#AdvArchMobile
Defensive Copying
data class Entity
private constructor(var private _date: Date) {
companion object {
fun create(date: Date): Entity =
Entity(_date = Date(date.time))
}
var date: Date = Date(_date.time)
get() = Date(field.time)
set(value) {
field = Date(date.time)
}
}

#AdvArchMobile
Presentation Logic
fun Date.relativeDateFormat(origin: Date = Date()): String { 
fun differenceInDays(date1: Date, date2: Date): Long { 
val MILLISECONDS_IN_A_DAY = 24 * 60 * 60 * 1000 
return (date1.time - date2.time) /
MILLISECONDS_IN_A_DAY 
} 
 
val daysAgo = differenceInDays(origin, this) 
return when { 
daysAgo < 0 -> "In the future" 
daysAgo < 1 -> "Today" 
daysAgo < 7 -> "Less than a week ago" 
daysAgo < 30 -> "Less than a month ago" 
daysAgo < 365 -> "Less than a year ago" 
else -> "Long time ago" 
} 
}

#AdvArchMobile
But
★ A class cannot implement an interface using
extensions
★ Methods are declared independently

#AdvArchMobile
Observation
data class ProductRequest(var name: String, var units: Int)
class Presenter() {
var request: ProductRequest by Delegates.observable(ProductRequest(name="",
units=0)) {
prop, old, new ->
requestChanged()
}
fun requestChanged() { print("Request: $request”) }
fun changeDoesNotTrigger() {
request.name = "Something"
request.units = 1
}
fun completeChangeThatTriggers() {
request = ProductRequest(name="Else", units= 2)
}
}

#AdvArchMobile
Delegating Reference
Type
class WeakReferenceHolder<T, U> { 
private var propertyRef: WeakReference<U>? = null 
 
operator fun getValue(t: T, property: KProperty<*>): U? =
propertyRef?.get() 
 
operator fun setValue(t: T, property: KProperty<*>, newValue: U?)
{ 
propertyRef = if (newValue != null) { 
WeakReference(newValue) 
} else { 
null 
} 
} 
} 
var view: ProgrammersListView? by
WeakReferenceHolder<ProgrammersListPresenter, ProgrammersListView>()

#AdvArchMobile
Avoid Enums
★ Space
★ Performance
Sealed
Classes
Too!

#AdvArchMobile
Don’t*
sealed class Interactor {
class ShowProducts(val completion: ()-
>Unit): Interactor() {}
class DeleteProduct(id: String,
completion: ()->Unit) {}
}
when (interactor) {
is ShowProducts -> …
}

#AdvArchMobile
Do
sealed class Result<V: Any, E:
Exception> {
class Success<V: Any, E:
Exception>(val value: V) : Result<V,
E>() {//…}
class Failure<V: Any, E:
Exception>(val error: E) : Result<V,
E>() {//…}
}

#AdvArchMobile
Recap
★ Kotlin makes advanced architectures easier
★ Learn your options and choose
★ Still learning the idioms, work with the
community

Home Improvement: Architecture & Kotlin

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