Singleton pattern

In <a href="/facts/Object-oriented_programming/TxNMEcao">object-oriented programming</a>, the singleton pattern is a <a href="/facts/Software_design_pattern/mV7r4egw">software design pattern</a> that restricts the <a href="/facts/Instantiation_(computer_science)/5zPBGdX1">instantiation</a> of a <a href="/facts/Class_(computer_programming)/zvzkSAtE">class</a> to a singular instance. It is one of the well-known <a href="/facts/Design_Patterns/sYDxSGc9">"Gang of Four" design patterns</a>, which describe how to solve recurring problems in object-oriented software. The pattern is useful when exactly one object is needed to coordinate actions across a system.
More specifically, the singleton pattern allows classes to:

<ul><li>Ensure they only have one instance</li>
<li>Provide easy access to that instance</li>
<li>Control their instantiation (for example, hiding the <a href="/facts/Constructor_(object-oriented_programming)/8JNHsH5H">constructors</a> of a <a href="/facts/Class_(computer_programming)/zvzkSAtE">class</a>)</li></ul>
The term comes from the <a href="/facts/Singleton_(mathematics)/LtNVfujT">mathematical concept of a singleton</a>.

Singleton pattern open-in-new

Singleton pattern