implementing-command-patterns

What problem does it solve?

Advanced guidance for implementing command patterns in CLI applications to improve maintainability, testability, and reliability.

Core Features & Use Cases

• Command struct pattern that encapsulates state, dependencies, and validated inputs.
• preRun patterns for parameter validation, flag binding to struct fields, and environment-variable fallbacks.
• run method structure with clear separation of concerns, deterministic behavior, and testable outputs.
• JSON output support and error handling patterns that adapt to output modes.
• Use Case: refactor a messy CLI into a consistent, well-tested command structure.

Quick Start

Create a new command following the patterns in this guide and bind flags directly to struct fields so preRun has immediate access to validated values.