Structural

Adapter

Allows incompatible interfaces to work together.

Legacy code integrationThird-party librariesAPI wrappers

Understanding Adapter

The Adapter pattern allows two incompatible interfaces to work together by wrapping one interface with another that the client expects. In Go, this is implemented by creating a struct that embeds or holds a reference to the adaptee and implements the target interface, translating method calls between the two. This is one of the most commonly used patterns when integrating third-party libraries or legacy code into a system that expects a different API.

Key Concepts

  • •Target interface — the interface the client code expects to work with
  • •Adaptee — the existing class or service with an incompatible interface that needs to be adapted
  • •Adapter struct — wraps the adaptee and implements the target interface, translating calls between the two
  • •No source modification — neither the client nor the adaptee code needs to change — only the adapter is new code

When to Use

✅ Use when
  • • Integrating a third-party library with a different API than yours
  • • Wrapping legacy code to work with new interfaces
  • • You want to create a reusable class that works with unrelated classes
  • • You need to use several subclasses but can't adapt their interfaces by subclassing
⚠️ Avoid when
  • • You can modify the source of the incompatible class directly
  • • The interfaces are only slightly different — a simple wrapper may suffice
  • • Too many adapters indicate a architectural mismatch that should be redesigned

Structure

Client
↓ calls Target interface
Adapter (implements Target)
↓ translates and delegates
Adaptee (incompatible interface)

How It Works

Client
expects: Play()
✕
Incompatible!
Adapter
Play() → PlayMP3()
Service
has: PlayMP3()
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Incompatible Interface

Client expects interface A but service provides interface B.

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Basic Implementation

Adapting a legacy MP3 player to a modern interface:

main.go
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Real-World Example: Logger Adapter

Integrating a third-party logging library with your application's interface:

main.go
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