objectType

An object type is a classification used in computing to describe the set of objects that share the same structure and behavior. It defines the data fields (attributes) that objects of this type can hold and the operations (methods) that can be performed on them. In object-oriented programming, object types are typically implemented by classes and interfaces, though other language constructs such as structs or records may serve a similar role. The object type establishes the interface and the contract that all instances must satisfy.

Typing and representation of object types vary by language. In statically typed languages, the object type is checked at compile time to ensure that method calls and field accesses are valid. In dynamically typed languages, these checks are deferred to runtime, often using duck typing or reflection. Some languages treat the type itself as a first-class value, enabling runtime inspection and manipulation of type objects or metaclasses.

Object types participate in subtyping and polymorphism, enabling code to operate on a range of objects through a common interface. Nominal typing relies on explicit declarations to establish subtyping, while structural typing determines compatibility from the shape of the type (the presence of required methods and properties). Examples include class hierarchies and interfaces in Java or C#, and Go’s interfaces or TypeScript’s structural interfaces.

In database systems that support object-relational features, an object type defines a user-created type with attributes and possibly methods, usable as a column type or in table definitions (for example, in Oracle). This blends data modeling with object-oriented concepts, allowing complex data to be stored and manipulated as a single unit.

Understanding object types helps in API design, data modeling, and ensuring interoperability across software components.