OptionBoolean

OptionBoolean is a type construct used in programming and data modeling to represent a boolean value that may be present or absent. It combines the boolean domain with an option or nullable type, allowing three observable states: true, false, and unknown or not provided. This is useful in APIs, configurations, and databases where a boolean field may be omitted or unspecified.

In languages with option types, Option<bool> (or Optional[Bool]) is implemented as a sum type with constructors for Some(true), Some(false), and None. Some(true) indicates an explicit true, Some(false) an explicit false, and None a lack of value. In languages without an explicit option type, it can be modeled with a nullable Boolean, where a null value represents absence.

Common operations on an OptionBoolean include checking for presence, providing default values, and mapping to other types or combining with other optional values. When serialized, JSON and similar formats typically encode None as null, Some(true) as true, and Some(false) as false.

Typical use cases include fields in user settings or API payloads that may be unspecified, tri-state flags where three outcomes are meaningful, and partial updates where a missing value should not overwrite existing data. OptionBoolean helps distinguish between an explicit false and a missing value, supporting more nuanced data handling and safer defaulting behavior.

See also: Option type, Maybe, Nullable, tri-state logic, optional value.