Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs Dependency Injection on Android Pedro Vicente Gómez Sánchez Senior Android Developer at Karumi [email protected] @pedro_g_s github.com/pedrovgs
Jul 02, 2015
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection on AndroidPedro Vicente Gómez SánchezSenior Android Developer at Karumi
[email protected]@pedro_g_sgithub.com/pedrovgs
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Alberto GrageraTechnical Director
Jorge BarrosoSenior Android Developer
Davide MendoliaSenior Full Stack Engineer
Sergio GutierrezSenior Full Stack Engineer
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Agenda● Introduction.
● What can I do using Dependency Injection?
● Scoped Graphs.
● Dagger on Android.
● Dagger 2.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
IntroductionInversion of Control
vs
Dependency Inversion
vs
Dependency Injection
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Inversion of Control
The natural evolution of the structured and imperative programming and the usage of reusable frameworks.
The execution point where you software takes the control is not defined by your software.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Inversion
One of the most important S.O.L.I.D principles.
Depend on abstractions, forget about implementation details.
Provide implementation details depending on abstractions can be tedious.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection
Software Design Pattern used to facilitate the usage of Dependency Inversion.
Provides dependencies given some previous configuration where abstractions are linked with
concretions.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Why?
The usage of IoC, Dependency Inversion and Dependency Injection provides give us the following benefits:
● Testability.● Decoupling.● Modularity.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Show me the code!
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection Example
The presenter inside this fragment has to be instantiated with all the dependency tree. Without a dependency
injector this can be tedious.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection Example
All the dependencies are passed in construction.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection Example
The implementation details are part of the Dependency Injector configuration.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dependency Injection Example
Now the Presenter is injected into the Fragment.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do with a Dependency Injector?
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?● Do not link the class to the runtime lifecycle or frameworks.
● Improve testability.
● Decouple your code and improve our software design.
● Detect code smells related to class dependencies and SRP violations.
● Change the implementation details in build time.
● Extract implementation details out of the business logic.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Do not link the class to the runtime lifecycle.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Improve testability.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Detect code smells related to class dependencies and single responsibility principle violations.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Change the implementation details in build time.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Decouple your code and improve our software design.
Using a Dependency Injector combined with the correct usage of Dependency Inversion we can easily develop the same feature at the
same time in different teams and layers.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Extract implementation details out of the business logic.
Develop software being agnostic of the Framework or the Runtime used. Implementation details are provided using the dependency injector and
your business logic does not depend on it.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?The dependency container provide us different configurations to provide dependencies:
● Singletons.
● Lazy Initialization.
● Provided dependencies.
● Named dependencies.
● Override dependencies already configured.
● Custom qualifiers.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Singletons
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Lazy Initialization
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Provided dependencies
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Named Dependencies
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
What can I do?Custom Qualifiers
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Scoped Graphs
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Scoped Graphs
Dependencies provided by the Dependency Container or Object Graph inside the Application class are linked to the Application lifecycle.
We need more than one graph to improve the Dependency Injector usage and performance.
At the same time, some dependencies are needed just when some components like Activities or Custom Views are initialized.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Scoped Graphs
Application Graph
Activity A Graph
Activity B Graph
Create Activity A
Create Activity B
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on Android
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 1. Add Dagger and Dagger Compiler as dependencies:
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 2. Create an Application extension and configure the Object Graph:
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 3. Configure Dagger Modules:
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 4. Initialize your Application Object Graph:
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 5. Create a method to extend the Application Object Graph:
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger on AndroidStep 6. Create a BaseActivity with the code needed to extend the
Application Graph.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Step 7. Create an abstract method requesting the Activity modules:
Dagger on Android
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Step 8. Extend the Application Object Graph using the Activity modules:
Dagger on Android
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
https://www.github.com/pedrovgs/EffectiveAndroidUI
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Can you repeat, please?
Dependency Injection on Android Workshop
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger 2
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Dagger 2
● Configuration based on components not in graphs.
● Generated code is now something you can read.
● Reflection free.
● 13 % faster.
● Full graph validated in build time.
Pedro V. Gómez Sánchez - [email protected] - @pedro_g_s - github.com/pedrovgs
Questions?