![Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved.
MacWire
● Generate instance creation code with constructor injection by macro
● Rich features (e.g. multi binding, tagged binding, intercepter, etc)
● No boilerplate
● All necessary components must be in the same scope
Create instance using wire[T] macro](https://image.slidesharecdn.com/revisitdependencyinjectioninscala-191028011004/85/Revisit-Dependency-Injection-in-scala-9-320.jpg)
Revisit Dependency Injection in scala
- 1. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Revisit Dependency Injection in Scala Naoki Takezoe @takezoen at Airframe Meetup #3
- 2. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. What’s Dependency Injection? ● Inversion of Control ● Externalize components dependency and make it configurable ● Encourage clean components design ● Components can be replaced (e.g. for testing) ● Good collaboration with Aspect Oriented Programming
- 3. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Dependency Injection in Java Explicit configuration to Less configuration
- 4. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Dependency Injection in Scala ● Java based DI container ○ Google Guice ● Pure Scala approach ○ Implicit parameter ○ Cake Pattern ○ Reader Monad, etc ● Scala native DI library ○ MacWire ○ Airframe
- 5. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Google Guice ● Widely used in Scala because of Play Framework ● Easy to use and understand ● Lack of Scala specific functionality Define binding in Module Use @Inject annotation for DI
- 6. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Implicit parameter ● No external library is required ● Easy to use and understand ● All necessary components must be in the same scope Take necessary components as implicit parameter Define necessary implicit val or def in the execution scope
- 7. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Cake Pattern ● No external library is required ● Boilerplate Combine by mix-in Declare dependency as self-type annotation
- 8. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Reader Monad ● Carry components around as an environment ● Need to put all necessary components together into the environment Run with environment
- 9. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. MacWire ● Generate instance creation code with constructor injection by macro ● Rich features (e.g. multi binding, tagged binding, intercepter, etc) ● No boilerplate ● All necessary components must be in the same scope Create instance using wire[T] macro
- 10. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Airframe ● Constructor injection and In-trait injection ● Rich features (e.g. tagged binding, type alias binding, config binding, etc) ● Less configuration by automatic instance creation ● Life-cycle management In-trait injection Define binding on Design if you need to override default binding
- 11. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Runtime DI vs Compile-time DI ● Runtime DI ○ Google Guice ○ Airframe ● Compile-time ID ○ Pure Scala approaches ○ MacWire
- 12. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. Runtime DI vs Compile-time DI Runtime DI Compile-time DI Binding error Runtime error Compilation error Configuration Less configuration Boilerplate is necessary Life-cycle management Yes No Overhead Runtime Compile-time External library Required Not required / Required Scala specific features Yes / No Yes
- 13. Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved. What approach is the best? ● Do you need auto-wiring? ● Which do you need? compile-time dependency check or dynamic-type binding? ● Do you need object life-cycle management?
- 14. Thank You! Danke! Merci! 谢谢! ありがとう! Gracias! Kiitos! Copyright 1995-2019 Arm Limited (or its affiliates). All rights reserved.