3.2 Strategy

  • Strategy
  • We use this pattern when we need to have several ways of doing the same thing. For example, we might want to sort a list using as little temporary memory as possible. Or our constraint might be CPU, in which case we would want to replace our sorting algorithm with one that performs better. We also see some of the drawbacks of using the strategy pattern by studying the AWT layout managers.

    • Converting switch statements
    • When writing code, we should avoid using if-else or switch. Every time we have a condition, we double the state space. This makes it hard to test our code. Much better is to encapsulate the functionality into strategy objects. In this part we learn how to convert a switch statement into the strategy pattern, thus reducing cyclomatic complexity and making it easier to test our code.

    • Intrinsic vs Extrinsic State
    • We look at ways to reduce the intrinsic state of strategy objects, so that we can share them between different contexts. We do this by converting extrinsic state to intrinsic.