![Template Method](/images/patterns/cards/template-method-mini.png?id=9f200248d88026d8e79d0f3dae411ab4)
Template Method em C#
O Template Method é um padrão de projeto comportamental que permite definir o esqueleto de um algoritmo em uma classe base e permitir que as subclasses substituam as etapas sem alterar a estrutura geral do algoritmo.
Complexidade:
Popularidade:
Exemplos de uso: O padrão Template Method é bastante comum nos frameworks C#. Os desenvolvedores costumam usá-lo para fornecer aos usuários do framework um meio simples de estender a funcionalidade padrão usando herança.
Identificação: O Template Method pode ser reconhecido por métodos comportamentais que já possuem um comportamento “padrão” definido pela classe base.
Exemplo conceitual
Este exemplo ilustra a estrutura do padrão de projeto Template Method. Ele se concentra em responder a estas perguntas:
- De quais classes ele consiste?
- Quais papéis essas classes desempenham?
- De que maneira os elementos do padrão estão relacionados?
Program.cs: Exemplo conceitual
using System;
namespace RefactoringGuru.DesignPatterns.TemplateMethod.Conceptual
{
// The Abstract Class defines a template method that contains a skeleton of
// some algorithm, composed of calls to (usually) abstract primitive
// operations.
//
// Concrete subclasses should implement these operations, but leave the
// template method itself intact.
abstract class AbstractClass
{
// The template method defines the skeleton of an algorithm.
public void TemplateMethod()
{
this.BaseOperation1();
this.RequiredOperations1();
this.BaseOperation2();
this.Hook1();
this.RequiredOperation2();
this.BaseOperation3();
this.Hook2();
}
// These operations already have implementations.
protected void BaseOperation1()
{
Console.WriteLine("AbstractClass says: I am doing the bulk of the work");
}
protected void BaseOperation2()
{
Console.WriteLine("AbstractClass says: But I let subclasses override some operations");
}
protected void BaseOperation3()
{
Console.WriteLine("AbstractClass says: But I am doing the bulk of the work anyway");
}
// These operations have to be implemented in subclasses.
protected abstract void RequiredOperations1();
protected abstract void RequiredOperation2();
// These are "hooks." Subclasses may override them, but it's not
// mandatory since the hooks already have default (but empty)
// implementation. Hooks provide additional extension points in some
// crucial places of the algorithm.
protected virtual void Hook1() { }
protected virtual void Hook2() { }
}
// Concrete classes have to implement all abstract operations of the base
// class. They can also override some operations with a default
// implementation.
class ConcreteClass1 : AbstractClass
{
protected override void RequiredOperations1()
{
Console.WriteLine("ConcreteClass1 says: Implemented Operation1");
}
protected override void RequiredOperation2()
{
Console.WriteLine("ConcreteClass1 says: Implemented Operation2");
}
}
// Usually, concrete classes override only a fraction of base class'
// operations.
class ConcreteClass2 : AbstractClass
{
protected override void RequiredOperations1()
{
Console.WriteLine("ConcreteClass2 says: Implemented Operation1");
}
protected override void RequiredOperation2()
{
Console.WriteLine("ConcreteClass2 says: Implemented Operation2");
}
protected override void Hook1()
{
Console.WriteLine("ConcreteClass2 says: Overridden Hook1");
}
}
class Client
{
// The client code calls the template method to execute the algorithm.
// Client code does not have to know the concrete class of an object it
// works with, as long as it works with objects through the interface of
// their base class.
public static void ClientCode(AbstractClass abstractClass)
{
// ...
abstractClass.TemplateMethod();
// ...
}
}
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Same client code can work with different subclasses:");
Client.ClientCode(new ConcreteClass1());
Console.Write("\n");
Console.WriteLine("Same client code can work with different subclasses:");
Client.ClientCode(new ConcreteClass2());
}
}
}
Output.txt: Resultados da execução
Same client code can work with different subclasses:
AbstractClass says: I am doing the bulk of the work
ConcreteClass1 says: Implemented Operation1
AbstractClass says: But I let subclasses override some operations
ConcreteClass1 says: Implemented Operation2
AbstractClass says: But I am doing the bulk of the work anyway
Same client code can work with different subclasses:
AbstractClass says: I am doing the bulk of the work
ConcreteClass2 says: Implemented Operation1
AbstractClass says: But I let subclasses override some operations
ConcreteClass2 says: Overridden Hook1
ConcreteClass2 says: Implemented Operation2
AbstractClass says: But I am doing the bulk of the work anyway