Empty interface
any is a type or type constraint that permits values of arbitrary concrete types without requiring a more specific interface or representation.
Go in Practice, Second Edition
any is a predeclared Go type alias for the empty interface type interface{}, allowing values of any type.
- How it is used
- Holds values of varied types in slices and JSON data whose structure is not known ahead of time.
- How deep it goes
- Defines the zero-method interface and works through JSON decoding and type inspection, while identifying its lack of type constraints.
- Examples
- Shows an integer-filled `[]interface{}` shuffle slice and JSON decoded into values accessed through `map[string]interface{}`.
- What you can do after
- Apply it via `encoding/json` to decode unknown JSON structures and inspect values with type assertions or switches.
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Build and Orchestrator in Go (From Scratch)
An empty interface is a Go interface type that imposes no method requirements and can hold a value of any type.
- How it is used
- Decouples a task manager from a concrete map or datastore by allowing Store methods to exchange values of different types.
- How deep it goes
- Explains flexible method signatures, concrete type assertions, comma-ok checks, and conversions, but stops short of broader type-system treatment.
- Examples
- Uses task.Task and task.TaskEvent values, Store methods, an in-memory map, and manager conversions from interface{}.
- What you can do after
- Apply it via Go type assertions to implement flexible Store boundaries and safely recover concrete task values.
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100 Go Mistakes and How to Avoid Them
any is a predeclared Go alias for interface{} that can hold a value of any type.
- How it is used
- Guides API design by limiting `any` to genuinely type-agnostic operations and favoring expressive concrete signatures elsewhere.
- How deep it goes
- Explains the alias, loss of type information, API trade-offs, explicit alternatives, and JSON numeric conversion, but not interface internals.
- Examples
- Uses heterogeneous assignments, an unexpressive Store API, explicit Store methods, `json.Marshal`, SQL query arguments, and JSON maps.
- What you can do after
- Evaluate API signatures, replace unnecessary `any` with explicit types, and diagnose JSON map values before making type assumptions.
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Learn Go with Pocket-Sized Projects
any is Go's predeclared constraint that permits any type as a generic type argument and is equivalent to interface{}.
- How it is used
- Supports reusable generic functions, structures, and variables when the implementation accepts values of any type.
- How deep it goes
- Defines any as an unconstrained type requirement and demonstrates explicit arguments, inference, and compilation of concrete instantiations.
- Examples
- Uses prettyPrint with float64 and string values, showing both explicit type arguments and compiler-inferred type arguments.
- What you can do after
- Build it from scratch: write generic Go functions that accept multiple concrete types and invoke them with explicit or inferred types.
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Related concepts
- contractkind of · An API contract is a specification of the operations, data, and behavioral expectations that govern interactions between software components.
- fmt.Printlnused by · fmt.Println is a Go standard-library function that writes its arguments separated by spaces and followed by a newline.
- Mapused by · A map is an associative data structure that stores key-value pairs and supports retrieving values by key.
- genericsalternative to · Generics are programming-language constructs that parameterize or generalize types and operations so they can apply to multiple concrete types or input forms.
- type constraintkind of · A type constraint is a rule that restricts admissible types or type arguments by requiring specified relationships, structures, properties, or supported operations.
- natural language interfacekind of · A natural language interface enables interaction with a system through human-language text or speech.
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