User-defined type
A user-defined type is a type declared by a user or programmer rather than supplied as a built-in type.
Learn Go with Pocket-Sized Projects
A custom type is a programmer-defined Go type that gives a distinct name and type identity to an underlying representation.
- How it is used
- Uses named types to clarify parameter meanings, domain fields, and package APIs.
- How deep it goes
- Works through declarations, typed calls, private fields, parsing, and validation; does not examine runtime type internals.
- Examples
- Shows language-coded greetings, a privately represented Decimal, and separately typed habit IDs, names, and weekly frequencies.
- What you can do after
- Build it from scratch with Go type declarations and typed fields, then add construction or validation where values need constraints.
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Go in Action, Second Edition
A defined type is a programmer-declared type that creates a distinct named type with an underlying type and can have its own methods.
- How it is used
- Models recipe-domain concepts with distinct names so intent is clearer and accidental misuse can be caught at compile time.
- How deep it goes
- Defines the declaration syntax, contrasts defined types with aliases, and develops struct and collection types into a recipe model.
- Examples
- Uses measurement magnitudes and units, ingredient lists, recipe steps, and a grocery list.
- What you can do after
- Build it from scratch: define domain-specific Go types and compose them into a recipe model with shared behavior.
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ScyllaDB in Action
A user-defined type is a named custom data type whose fields can have different types and that can be used as a column, collection element, or key value in ScyllaDB.
- How it is used
- Groups related, differently typed properties into one value for schemas such as contact details and image metadata.
- How deep it goes
- Defines creation, insertion, null behavior, frozen collection use, and Python driver mapping; defers required-field enforcement to application code.
- Examples
- Uses contact_info fields and an image type with path and caption in an article image gallery.
- What you can do after
- Apply it via CQL schemas and Python driver registration to store and retrieve structured image metadata.
Spring in Action, Sixth Edition
A Cassandra user-defined type is a schema-defined composite type whose fields can be stored together in a column.
- How it is used
- Stores denormalized composite data, especially copied related records inside Cassandra collection columns.
- How deep it goes
- Explains collection constraints, denormalization, annotation, separate classes, and optional fields without covering schema operations.
- Examples
- Uses taco ingredients, IngredientUDT, TacoUDT, and a stored ingredient collection as concrete mapping examples.
- What you can do after
- Build it from scratch by defining a separate annotated UDT class for structured values embedded in Cassandra columns.
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React in Depth
A custom type is a programmer-defined type specification that restricts or describes the values permitted in a program.
- How it is used
- Constrains variables, function results, and React component props to documented value shapes.
- How deep it goes
- Explains unions, literal values, interfaces, optional properties, and unknown, but defers technical differences between interfaces and type aliases.
- Examples
- Uses nullable names, status literals, invalid assignments, and typed React component props with optional fields.
- What you can do after
- Apply it via TypeScript to reject invalid values and document React component interfaces.
Related concepts
- type aliascontrasts with · A type alias is a declaration that gives an existing type an alternative name without creating a distinct type or representation.
- ingredientincludes · An ingredient is a material or item used as an input in preparing a product, dish, or completed work.
- atomic typekind of · An atomic type is a type whose supported accesses and operations are indivisible with respect to concurrent execution and provide defined synchronization semantics.
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