The Template Method Pattern defines the skeleton of algorithm in a method, define some steps to
subclasses. Template Method lets subclass redefine certain steps of an algorithm without changing
the algorithm's structrue.
Class diagram:
abstract class AbstractClass{
final void templateMethod(){
primitiveOperation1();
primitiveOperation2();
concreteOpration();
}
abstract void primitiveOperation1();
abstract void primitiveOperation2();
void concreteOperation(){
// implementation here
}
void hook(){}
}
A hook is a method that is declared in the abstract class, but only given an empty or default implementation,use hooks
when that part of the algorithm is optional, with hooks, a subclass may choose to implement that hook, but it doesn't have to.
The Hollywood Priciple:
- Don't call us, we'll call you
the Hollywood principle gives us a way to prevent "dependency rot". Dependency rot happens when you have high-level
components depending on low-level components.
The Strategy and Template Method Patterns both encapsulate algorithms, one by inheritance and one by composition.