In computer programming, the strategy pattern (also known as the policy pattern) is a particular software design pattern, whereby algorithms behaviour can be selected at runtime. Formally speaking, the strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
For instance, a class that performs validation on incoming data may use a strategy pattern to select a validation algorithm based on the type of data, the source of the data, user choice, and/or other discriminating factors. These factors are not known for each case until run-time, and may require radically different validation to be performed. The validation strategies, encapsulated separately from the validating object, may be used by other validating objects in different areas of the system (or even different systems) without code duplication.
The essential requirement in the programming language is the ability to store a reference to some code in a data structure and retrieve it. This can be achieved by mechanisms such as the native function pointer, the first-class function, classes or class instances in object-oriented programming languages, or accessing the language implementation's internal storage of code via reflection.
Read more about Strategy Pattern: Example, Strategy and Open/closed Principle
Famous quotes containing the words strategy and/or pattern:
“That is the way of youth and life in general: that we do not understand the strategy until after the campaign is over.”
—Johann Wolfgang Von Goethe (1749–1832)
“His talent was as natural as the pattern that was made by the dust on a butterfly’s wings. At one time he understood it no more than the butterfly did and he did not know when it was brushed or marred. Later he became conscious of his damaged wings and of their construction and he learned to think and could not fly any more because the love of flight was gone and he could only remember when it had been effortless.”
—Ernest Hemingway (1899–1961)