Singleton pattern

In software engineering, the singleton pattern is a software design pattern that restricts the instantiation of a class to a singular instance. One of the well-known "Gang of Four" design patterns, which describes how to solve recurring problems in object-oriented software,^[1] the pattern is useful when exactly one object is needed to coordinate actions across a system.

More specifically, the singleton pattern allows objects to:^[2]

• Ensure they only have one instance
• Provide easy access to that instance
• Control their instantiation (for example, hiding the constructors of a class)

The term comes from the mathematical concept of a singleton.