Nullable type
A nullable type is a type whose values may be either a value of the underlying type or an explicit representation of absence, such as null.
Kotlin in Action, 2E
A nullable type is a type whose values may include null and whose unsafe operations are restricted by the type system.
- How it is used
- Prevents potential NullPointerExceptions by making absent values explicit in Kotlin APIs and expressions.
- How deep it goes
- Develops syntax, checks, operators, collections, generics, nullable extensions, primitive representation, and Java overrides.
- Examples
- Uses string-length functions, optional ages, parsed-number lists, nullable receiver extensions, and Java interface implementations.
- What you can do after
- Apply nullable types and Kotlin null-handling operators to prevent unsafe dereferences and model absent values.
Pro ASP.NET Core 7, Tenth Edition
A nullable parameter type is a parameter type that permits a null value to represent the absence of a supplied argument.
- How it is used
- Distinguishes missing ASP.NET Core request values from supplied values and permits unassigned form properties to participate in validation.
- How deep it goes
- Works through compiler warnings, array declarations, and a controller query without detailing model-binding internals.
- Examples
- Uses nullable product arrays, an optional controller ID tested with two URLs, and an RSVP attendance field.
- What you can do after
- Apply it via ASP.NET Core model binding to distinguish omitted IDs from supplied values and detect an unanswered required choice.
Read how Pro ASP.NET Core 7, Tenth Edition explains nullable type →
F# in Action: A Revised Edition of Get Programming with F#
Nullable<T> is a .NET value type that represents either a value of a non-nullable value type or the absence of such a value.
- How it is used
- Models absent values for .NET value types and supports safe conversion between .NET representations and F# options.
- How deep it goes
- Explains the modeling problem, historical solution, boundary conversions, and preferred F# usage without detailing Nullable<T> internals.
- Examples
- Uses magic integer values, SQL-originated missing numbers, and F# conversions for empty or populated Nullable values.
- What you can do after
- Apply it via F# Option conversion functions at .NET boundaries while keeping domain modeling centered on options.
Read how F# in Action: A Revised Edition of Get Programming with F# explains nullable type →
Related concepts
- Kotlinused by · Kotlin is a statically typed general-purpose programming language that targets the JVM and other platforms and interoperates with Java.
- non-nullable typecontrasts with · A non-nullable type is a type whose values are statically constrained not to include the null value.
- missing valueuses · A missing value is a marker or condition indicating that an expected data value or reference is absent, unavailable, unknown, or inapplicable.
- ..< operatoruses · The `..<` operator constructs a range that includes its lower endpoint and excludes its upper endpoint.
- operatoruses · An operator is a symbol, keyword, or language construct that specifies an operation on one or more operands.
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