Go Interfaces

Go Interfaces and Composition

Resource Routing

• scripts/check-interface-compliance.sh - Run as a heuristic to find exported interfaces that may need compile-time assertions.
• scripts/check-interface-compliance.go - Implementation helper invoked by check-interface-compliance.sh; patch this when changing method-set analysis.
• references/EMBEDDING.md - Read when embedding interfaces or structs in public APIs.
• references/RECEIVER-TYPE.md - Read when pointer/value receivers affect interface satisfaction.

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Accept Interfaces, Return Concrete Types

Interfaces belong in the package that consumes values, not the package that implements them. Return concrete (usually pointer or struct) types from constructors so new methods can be added without refactoring.

// Good: consumer defines the interface it needs
package consumer

type Thinger interface { Thing() bool }

func Foo(t Thinger) string { ... }

// Good: producer returns concrete type
package producer

type Thinger struct{ ... }
func (t Thinger) Thing() bool { ... }
func NewThinger() Thinger { return Thinger{ ... } }