How to Register Go Packages Without Creating Circular Dependencies?

Registering Packages in Go without Creating Circular Dependencies

Problem

Consider a central package providing interfaces that several other packages depend on. Each dependent package offers multiple implementations of these interfaces. The goal is to inform the central package about these implementations to enable client instantiation, but importing dependent packages in the central package creates a circular dependency.

Solution

The Go standard library offers two approaches to address this issue:

1. Without a "Central" Registry

• Define interfaces in the central package and encapsulate implementations in separate packages.
• Explicitly instantiate desired implementations, specifying the package name.
• Example: The crypto package defines the Hash interface, while concrete implementations are found in separate packages like crypto/md5 and crypto/sha256.

2. With a "Central" Registry

• Implementations register themselves in the central package, typically via package init() functions.
• Example: The image package defines the Image interface and multiple image format implementations in packages like image/gif and image/jpeg.

Alternative Solution (Proposed): "Custom" Registry

• Create a middleman package (e.g., pf) that imports both the central package (pi) and the implementation packages (e.g., pa, pb).
• Define "factory" methods in pf to instantiate clients, avoiding circular dependencies between pf and the other packages.

Recommendation

The best solution depends on the requirements. Option 1 is preferred if implementation selection can be made beforehand. Option 2 allows for extensibility, but requires explicit registration. Option 3 offers a compromise between convenience and extensibility.

The above is the detailed content of How to Register Go Packages Without Creating Circular Dependencies?. For more information, please follow other related articles on the PHP Chinese website!