DUTDIP - Don't Use This Dependency Injection
- 2. Opinions and emotions DUTDIP Interesting Go nuances & My Mistakes
- 3. Abstractions over Implementations Inject or Lookup Dependencies Lifecycle of Services and Dependencies Loose Coupling & Unit Testing Avoid Unutilized Dependencies
- 4. Code against interfaces Contracts & Data Model in a “model” package Ben Johnson’s “Root” package No cyclical dependencies References: https://medium.com/@benbjohnson/standard-package-layout-7cdbc8391fc1 https://appliedgo.net/di/ https://8thlight.com/blog/uncle-bob/2012/08/13/the-clean-architecture.html Credit: Robert Wechsler (www.robertwechsler.com) for permission to use image of “Circular Bike”.
- 5. Contracts to be implemented Service has a Dependency Sometimes, it also has Another-Dependency
- 6. Package-Level-New-Function (PLNF) for Service Consume Dependency from the instance member Typical Service initialization and invocation
- 7. Pass problem of implementations to Upper Layer Tight coupling, Upper Layer needs to “know”
- 8. Pass from top (main) package to that specific layer
- 9. Dependencies before Services Validation & Persistence example Why incur cost and allocate resources for unused dependencies?
- 10. Pass New Function Func type in Model Package Function not Instance New Instance then Invoke https://martinfowler.com/articles/injection.html#UsingAServiceLocator
- 11. Projects evolve, Requirements change Signature of “New” function can change Context class
- 12. Cant embed Functions in a Structure (Language feature request) Wrapper Method to a private member
- 13. Instantiate a Service, Invoke Operations Code is a bit tedious
- 14. Func types -> Package Level New Functions Orchestration, Package Level Variables Encapsulate to Structures Structure changes are backward compatible Hide behind Interfaces Flexibility and Extensibility Reference: ● https://dave.cheney.net/2017/06/11/go-without-package-scoped-variables
- 15. Dependency New Function -> Dependency Factory Structure Interface
- 16. Embed multiple Factories -> Super Factory No wrapper code Interface
- 17. Service expects Super Factory Invoke
- 18. Add Service to Super Factory Uniform invocation mechanism SuperFactory is parameter Pass SF to all Layers
- 19. Global Reference to SuperFactory in Model package Initialize Service Initialize Dependency
- 20. No Injection, Only Lookup Defer language syntax
- 21. Unit Testing using GoMock Create a Test Super Factory Can also embed other relevant data structures Initialize a Test-SF
- 23. Change my Factory implementation Create a Singleton Replace Embedding
- 24. Embed multiple structures Almost like Multiple Inheritance Can’t do it in Java or C# No wrapper Code
- 28. Many services & dependencies, centralization Changes in dependencies Extreme loose coupling, Unit Testing
- 29. • Package level New Functions • Pass Dependencies, Simple • Assign functions to Package Variables • Overwrite variables with Mock • Same benefits and limitations • Graph / Container • Definitions, Resolve • Reflection, Casting, Tighty coupling to variable • Duck Typing • Violation of Dependency Inversion principle References: ● Package New Function ○ https://appliedgo.net/di/ ○ https://medium.com/@zach_4342/dependency-injection-in-golang- e587c69478a8 ○ http://www.florinpatan.ro/2016/09/using-dependency-injection-pattern-
- 30. in-go.html ● Graphs & Containers ○ github.com/facebookgo/inject ○ github.com/karlkfi/inject ○ github.com/sarulabs/di ○ github.com/uber-go/dig ● Duck Typing ○ http://txt.fliglio.com/2015/04/di-duck-typing-and-clean-code-in-go/ ● New Functions Assigned to Variables: ○ http://openmymind.net/Dependency-Injection-In-Go/ ○ https://dave.cheney.net/2017/06/11/go-without-package-scoped- variables
- 31. Super Factory contains many items Restrict access to only the relevant factories Create a custom factory interface, Inherently compatible with SuperFactory