| name | dependency-injection |
| description | Wire dependencies using constructor-based dependency injection throughout services, repositories, and handlers. |
Dependency Injection & Construction
When to use this skill
- Wire services, repositories, and handlers with their dependencies
- Initialize core services during application bootstrap
- Pass dependencies to plugins during initialization
- Create dependency graphs that are testable and mockable
- Avoid service locators and global state
Key principles
- Constructor-based: Dependencies passed via function parameters
- Explicit over implicit: Dependencies visible in constructor signatures
- Interface-based: Depend on interfaces, not concrete implementations
- Single responsibility: Each constructor handles one entity's wiring
- Bootstrap concentrated: Wiring happens in bootstrap.go and plugin Init
Pattern
Dependency injection flow:
- Repositories accept bun.IDB and return interface
- Services accept repositories and return interface
- Use cases accept services and return struct
- Handlers accept use cases and return struct
- Plugins accept PluginContext, retrieve services, create dependencies
- No global state or service locators
Example
See examples/di_todo_example.go for:
- BuildTodosPlugin demonstrating complete DI chain
- Bottom-up wiring (Database ??? Repository ??? Service ??? UseCase ??? Handler)
- Dependency graph diagram
- Unidirectional dependency flow
Common mistakes
- Circular dependencies (Service A ??? Service B ??? Service A)
- Lazy initialization instead of bootstrap-time
- Depending on concrete types instead of interfaces
- Creating service instances multiple times
- Service retrieval without type assertion
- Not checking ok flag on type assertion
References
