Strategy

The Strategy pattern enables an object, called the context, to support variations in its logic by extracting the variable parts into separate, interchangeable objects called strategies. The context implements the common logic of a family of algorithms, while a strategy implements the mutable parts, allowing the context to adapt its behavior depending on different factors, such as an input value, a system configuration, or user preferences.

Strategies are usually part of a family of solutions and all of them implement the same interface expected by the context. The following figure shows the situation we just described:

Figure 9.1: General structure of the Strategy pattern

Figure 9.1 shows you how the context object can plug different strategies into its structure as if they were replaceable parts of a piece of machinery. Imagine a car; its tires can be considered its strategy for adapting to different road conditions. We...