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Objects are instances of a class. Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, [1] which can contain data and code: data in the form of fields (often known as attributes or properties), and code in the form of procedures (often known as methods).
Together this implies that a class in Smalltalk is an object and that, therefore a class needs to be an instance of a class (called metaclass). As an example, a car object c is an instance of the class Car. In turn, the class Car is again an object and as such an instance of the metaclass of Car called Car class. Note the blank in the name of ...
In object-oriented programming, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. It is one of the well-known "Gang of Four" design patterns , which describe how to solve recurring problems in object-oriented software. [ 1 ]
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
The object methods include access to the object state (via an implicit or explicit parameter that references the object) whereas class methods do not. If the language supports inheritance , a class can be defined based on another class with all of its state and behavior plus additional state and behavior that further specializes the class.
A language that supports creating an object from a class is classified as class-based. A language that supports object creation via a template object is classified as prototype-based. The concept of object is used in many different software contexts, including: Possibly the most common use is in-memory objects in a computer program written in ...
In knowledge representation, particularly in the Semantic Web, a metaclass is a class whose instances can themselves be classes. Similar to their role in programming languages, metaclasses in ontology languages can have properties otherwise applicable only to individuals, while retaining the same class's ability to be classified in a concept hierarchy.
Constructing different representation of independent complex objects. A class wants its subclass to implement the object it creates. The class instantiations are specified at run-time. There must be a single instance and client can access this instance at all times. Instance should be extensible without being modified.