Struct embedding
Struct embedding is a Go language feature that includes an anonymous field of one type in a struct and promotes the embedded type’s fields and methods.
100 Go Mistakes and How to Avoid Them
Type embedding is a Go language feature that promotes the fields and methods of an embedded type into the embedding type's method set and selector space.
- How it is used
- Uses embedding to reuse fields and methods while diagnosing unintended API visibility in Go structs.
- How deep it goes
- Explains selector promotion, receiver behavior, interface composition, and a mutex visibility failure, then stops short of broader embedding rules.
- Examples
- Uses Foo and Bar promotion, io.ReadWriter composition, an InMem mutex, and Logger forwarding or embedding.
- What you can do after
- Diagnose accidental method exposure and choose between embedded fields, named fields, and explicit forwarding methods.
Read how 100 Go Mistakes and How to Avoid Them explains struct embedding →
Go by Example
Field embedding is the inclusion of an anonymous field in a Go struct so the embedded field and its members can be promoted.
- How it is used
- Uses embedding to compose reusable HTTP middleware, satisfy interfaces, intercept methods, and extend behavior without modifying handlers.
- How deep it goes
- Explains promotion, forwarding, interface satisfaction, method hiding, and serialization hazards through an HTTP interceptor, while deferring broader pitfalls to type assertions.
- Examples
- Demonstrates an HTTP ResponseWriter interceptor, status-code logging middleware, curl requests, and resulting server logs.
- What you can do after
- Build composable Go types that promote methods, intercept selected behavior, satisfy interfaces, and preserve access to underlying capabilities.
Learn Go with Pocket-Sized Projects
Embedding is a Go struct feature that incorporates an unnamed field's type and promotes its methods and fields to the containing type.
- How it is used
- Uses embedding to compose Go types and satisfy generated interfaces, especially when implementing a gRPC server.
- How deep it goes
- Defines embedding through a server example and explains its required generated method, but does not explore method promotion mechanics in depth.
- Examples
- Uses Server, UnimplementedHabitsServer, Logger, and CreateHabit to demonstrate embedded and named fields together.
- What you can do after
- Build it from scratch by embedding a generated implementation and registering the containing server against its interface.
Read how Learn Go with Pocket-Sized Projects explains struct embedding →
Go in Action, Second Edition
Struct embedding is a Go language feature that embeds one struct type in another and promotes the embedded type's fields and methods.
- How it is used
- Uses embedding to build complex Go domain types through composition instead of class-based inheritance.
- How deep it goes
- Explains promotion and composition, then applies them to measurements and recipes without detailing compiler resolution or embedding rules.
- Examples
- Demonstrates embedded metric and imperial measurements inside a recipe application with conversion, scaling, and grocery-list generation.
- What you can do after
- Build domain models that reuse fields and methods through composition and extend behavior with wrappers and interfaces.
Read how Go in Action, Second Edition explains struct embedding →
Related concepts
- inheritancecontrasts with · Inheritance is a mechanism by which a child type or element receives properties, values, or behavior from a parent, subject to system rules and possible overrides.
- structpart of · A struct is a composite data type or structure that groups related fields or values into a single unit.
- compositionequivalent to · Composition is a technique for combining simpler functions, components, or operations into a larger structure or behavior.
- aspectused by · An aspect is a modular unit of cross-cutting behavior applied around selected program operations or method invocations.
- http.ResponseWriteruses · http.ResponseWriter is the Go interface through which an HTTP handler constructs a response by writing its headers, status, and body.
- Marshaler interfaceimplements · The Marshaler interface is a Go interface requiring a MarshalJSON method that supplies a type’s custom JSON encoding.
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