# Template ## What? * A Template method pattern provides a skeleton for performing any sort of algorithm or an operation, and it allows the sub-classes to re-define part of the logic. * Template Method uses inheritance to vary part of an algorithm * Template Method modifies the logic of an entire class. * Factory Method is a specialization of Template Method. ## When to use?? * When you want your program be "Open For Extension” and also “Closed for Modification” * When you face many same line of codes that are duplicated through deferring just some steps of your algorithm. * When you as a designer of a framework, want that your clients just to use any executable code that is passed as an argument to your framework, which is expected to call back (execute) that argument at a given time * Natural fit for building frameworks, so that parent framework classes can make callbacks into methods implemented in child * A template pattern should be used when there is an algorithm with many implementations ## Why use?? * Let subclasses implement varying behavior (through method overriding) * Avoid duplication in the code , the general workflow structure is implemented once in the abstract class’s algorithm, and necessary variations are implemented in the subclasses. * Control at what points subclassing is allowed. As opposed to a simple polymorphic override, where the base method would be entirely rewritten allowing radical change to the workflow, only the specific details of the workflow are allowed to change. ## Drawbacks * Debugging and understanding the sequence of flow in the Template Method pattern can be confusing at times. * in other more complex scenarios state can be scattered throughout many (sub-) classes and source files that has to be managed and maintained somehow. * instantiating objects to be able to call the methods is cumbersome. In general it is just an unwieldy construct. * the abuse of the Template Method pattern tends to generate into deep hierarchies of concrete classes * Instead, Favor object composition over class inheritance * use Strategy pattern * A lot of boiler-plate code involved ## Links * *