Template Method Pattern

In object-oriented programming, the template method is one of the behavioral design patterns identified by Gamma et al. in the book Design Patterns. The template method is a method in a superclass, usually an abstract superclass, and defines the skeleton of an operation in terms of a number of high-level steps. These steps are themselves implemented by additional helper methods in the same class as the template method.

The helper methods may be either abstract methods, for which case subclasses are required to provide concrete implementations, or hook methods, which have empty bodies in the superclass. Subclasses can (but are not required to) customize the operation by overriding the hook methods. The intent of the template method is to define the overall structure of the operation, while allowing subclasses to refine, or redefine, certain steps.

Wikipedia: Template Method Pattern


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abstract class Abstract {
  String abstractMethod();
  String hookMethod() => "OMG I am a hook!";
  void templateMethod() {

class Concrete extends Abstract {
  String abstractMethod() => "This is a boring example...";

class ConcreteOverridingHook extends Abstract {
  String abstractMethod() => "So, so boring...";
  String hookMethod() => "I'm an overriden hook method!";

void main() {
  var con1 = Concrete();
  var con2 = ConcreteOverridingHook();

    This is a boring example...
    OMG I am a hook!
    So, so boring...
    I'm an overriden hook method!