android clean architecture workshop 3h edition
TRANSCRIPT
#AndroidArch
#AndroidArch
Implementing Clean Architecture in
AndroidJorge D. Ortiz-Fuentes
@jdortiz
A Canonical Examples production
#AndroidArch
#AndroidArch
Agenda★Goals
★Before Clean Architecture
★Clean Architecture Concepts
★ Implementation rules
★Example App: RealProgrammers
★ Implement 1st User Story
★References
#AndroidArch
Full Version: 3d★MVX
• Learn
• Extract MVP
★1st User Story
• Use Case
• Presenter
• View
• Entity Gateway
• Initial connection
★Connectors
• Memory Management
• Reuse
★2nd user story: add
• Navigation: Modal vs Push
• Command pattern
• Immutables
• Observation
★3rd user story: detail
• Identity
• Use case factories
• 2nd use case in the same view
★Other use cases: just logic
★Forward flow synchronization
★Dependency Injection
★Asynchrony
• Async entity gateway
• Other tasks
#AndroidArch
LIVE Online Training★3 days (same weekday 3 continuous weeks)
★10 people max
★Live coding shared via video conference
★Chat running all the time
★Complete repo with many commits and Tests> 95%
★Additional exercises
★Ask as much as you want!
Goals
#AndroidArch
Goals
★Understand the concepts
★ Learn the sources
★ Implement the ideas of the Clean Architecture in a real app
★Grow from here
Looking for volunteer
Warning: Background Ahead!
Before Clean Architecture
#AndroidArch
Before Clean Architecture
★MVC
★MVP
★MVVM
– Martin Fowler
“Different people reading about MVC in different places take different ideas from it and describe these as 'MVC'. If this doesn't cause enough confusion you then get the effect of
misunderstandings of MVC that develop through a system of Chinese whispers.”
#AndroidArch
Tricky question★ If [Model] + [View] + [Controller /
Presenter / View Model] = [TheApp]
★How can Controller != Presenter != View Model?
★Responsibilities matter!
★Other components (patterns) might be involved.
#AndroidArch
The goal★Separation of responsibilities into roles. Is
it? Not historically. Other motivations. Solving problem d’jour.
★Now why?
• Testability
• Reusability
• Extensibility
#AndroidArch
MVC: The early days
★Separated presentation: Model <-> Presentation (= V+C)
★Observer originated from MVC, but observing full object (properties = scalars)
★Variations: Passive model, i.e. model cannot send updates (for example HTTP)
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Android’s MVC★View
• Only View subclasses
• Show information and handle events to controller
• Fully reusable library of views. Consistent L&F
★Controller
• Listeners+Watchers+Adapters control what’s displayed
• Receive the events and converts them into calls to the model
• Observe the model and update what is displayed on the view
• Implement presentation logic
★Model
• Implements domain knowledge / business logic. Provides data and commands
• Can be observed
• No references to the UI
•Flow synchronization vs Observer synchronization
Apple’s MVC
Ctrlr
ModelView
#AndroidArch
MVC: testability★The views are somebody else's (Google’s)
problem.
★Model is easy to test.
★Controller is huge & has dependencies on the model and on the views => Complex to test.
★Too many levels of abstraction, only a few methods exposed.
★Some stuff in activity that it is usually not tested.
MVP
MVP
Presenter ModelView
Events Operations
Changes Changes
MVVM
MVVM
View Model ModelView
Events & Info Operations
Changes Changes
Clean Architecture Concepts
#AndroidArch
Clean Architecture
★Uncle Bob’s (Robert C. Martin’s) architecture
★Based in Onion, in turn based in hexagonal, DCI and some others
Clean Architecture
View (A/F) Presenter Interactor Entity Gateway
Connector
Persistance FW
View
Netw
ork
Location FW
Presenter
Entity Gateway
Clean Architecture
Interactor
Entity
Implementation Rules
#AndroidArch
Rules★We are going to develop one module at a
time
★ Follow the dependency rules
★YAGNI
★No early optimization applied
★ It is easy to add tests, but no TDD in 3h OK??
Example App: RealProgrammers
#AndroidArch
Features★Add potential candidates (Name, email, and important skills)
★Show list of programmers with relative interview date
★Remove candidates from list
★Edit the data of any candidate
★Contact candidate by email
★Sync between devices
★Universal app (Fragments)
★Eye candy
★Android/Android Wear/Android TV/Google Glasses
★Credits
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MVP Features★Add potential candidates (Name, email, and important skills)
★Show list of programmers with relative interview date
★Remove candidates from list
★Edit the data of any candidate
★Contact candidate by email
★Sync between devices
★Universal app (Fragments)
★Eye candy
★Android/Android Wear/Android TV/Google Glasses
★Credits
Implementing the 1st User Story
I feel like I could Take On the
World!
#AndroidArch
First User Story
★Show a list of data elements to the user.
Interactor
View (A/F) Presenter Show Programmers
Entity Gateway
#AndroidArch
Interactor
★Grab data from the entity gateway
★Convert it to what is needed to be presented
★Pass the results to the presenter
★Start by defining the interfaces
Presenter
View (A/F) ProgrammersList
Show Programmers
Entity Gateway
#AndroidArch
Presenter
★Direction: only from interactor to view
★Configure the (dumb) view with the data provided to it
★Create the interface for the view (Simplest wins!)
View
Programmers ListActivity
ProgrammersList
Show Programmers
Entity Gateway
#AndroidArch
View
★Combination of Views + Activity
★Make it dumb (passive), but useful
★Tell the presenter about the relevant events
★Keep them decoupled
Presenter
Programmers ListActivity
ProgrammersList
Show Programmers
Entity Gateway
#AndroidArch
Back to the Presenter
★ Implement responses to the user events.
★Use the interactor
★Add presentation logic to the presenter part
#AndroidArch
Presentation Logic
★Date should be relative (“Today”, “1d ago”, “2w ago”)
★That means current date is a dependency that we want to control for tests
★Use lazy instantiation for the current date
Entity Gateway
Programmers ListActivity
ProgrammersList
Show Programmers
Entity Gateway
#AndroidArch
Entity Gateway
★Basic
★Defer the decision of the persistence framework for later.
★ Implement the minimum functionality in a basic object.
★ Implications of the repository pattern.
References
#AndroidArch
References
★http://martinfowler.com/eaaDev/uiArchs.html
★https://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html
★https://cleancoders.com/episode/clean-code-episode-7/show
Thank you!
@jdortiz #AndroidArch