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Builder

Builder en C#

Builder es un patrón de diseño creacional que permite construir objetos complejos paso a paso.

Al contrario que otros patrones creacionales, Builder no necesita que los productos tengan una interfaz común. Esto hace posible crear distintos productos utilizando el mismo proceso de construcción.

Uso del patrón en C#

Complejidad:

Popularidad:

Ejemplos de uso: El patrón Builder es muy conocido en el mundo C#. Resulta especialmente útil cuando debes crear un objeto con muchas opciones posibles de configuración.

Identificación: El patrón Builder se puede reconocer por la clase, que tiene un único método de creación y varios métodos para configurar el objeto resultante. A menudo, los métodos del Builder soportan el encadenamiento (por ejemplo, algúnBuilder->establecerValorA(1)->establecerValorB(2)->crear()).

Ejemplo conceptual

Este ejemplo ilustra la estructura del patrón de diseño Builder. Se centra en responder las siguientes preguntas:

  • ¿De qué clases se compone?
  • ¿Qué papeles juegan esas clases?
  • ¿De qué forma se relacionan los elementos del patrón?

Program.cs: Ejemplo conceptual

using System;
using System.Collections.Generic;

namespace RefactoringGuru.DesignPatterns.Builder.Conceptual
{
    // The Builder interface specifies methods for creating the different parts
    // of the Product objects.
    public interface IBuilder
    {
        void BuildPartA();
		
        void BuildPartB();
		
        void BuildPartC();
    }
    
    // The Concrete Builder classes follow the Builder interface and provide
    // specific implementations of the building steps. Your program may have
    // several variations of Builders, implemented differently.
    public class ConcreteBuilder : IBuilder
    {
        private Product _product = new Product();
        
        // A fresh builder instance should contain a blank product object, which
        // is used in further assembly.
        public ConcreteBuilder()
        {
            this.Reset();
        }
        
        public void Reset()
        {
            this._product = new Product();
        }
		
        // All production steps work with the same product instance.
        public void BuildPartA()
        {
            this._product.Add("PartA1");
        }
		
        public void BuildPartB()
        {
            this._product.Add("PartB1");
        }
		
        public void BuildPartC()
        {
            this._product.Add("PartC1");
        }
		
        // Concrete Builders are supposed to provide their own methods for
        // retrieving results. That's because various types of builders may
        // create entirely different products that don't follow the same
        // interface. Therefore, such methods cannot be declared in the base
        // Builder interface (at least in a statically typed programming
        // language).
        //
        // Usually, after returning the end result to the client, a builder
        // instance is expected to be ready to start producing another product.
        // That's why it's a usual practice to call the reset method at the end
        // of the `GetProduct` method body. However, this behavior is not
        // mandatory, and you can make your builders wait for an explicit reset
        // call from the client code before disposing of the previous result.
        public Product GetProduct()
        {
            Product result = this._product;

            this.Reset();

            return result;
        }
    }
    
    // It makes sense to use the Builder pattern only when your products are
    // quite complex and require extensive configuration.
    //
    // Unlike in other creational patterns, different concrete builders can
    // produce unrelated products. In other words, results of various builders
    // may not always follow the same interface.
    public class Product
    {
        private List<object> _parts = new List<object>();
		
        public void Add(string part)
        {
            this._parts.Add(part);
        }
		
        public string ListParts()
        {
            string str = string.Empty;

            for (int i = 0; i < this._parts.Count; i++)
            {
                str += this._parts[i] + ", ";
            }

            str = str.Remove(str.Length - 2); // removing last ",c"

            return "Product parts: " + str + "\n";
        }
    }
    
    // The Director is only responsible for executing the building steps in a
    // particular sequence. It is helpful when producing products according to a
    // specific order or configuration. Strictly speaking, the Director class is
    // optional, since the client can control builders directly.
    public class Director
    {
        private IBuilder _builder;
        
        public IBuilder Builder
        {
            set { _builder = value; } 
        }
        
        // The Director can construct several product variations using the same
        // building steps.
        public void buildMinimalViableProduct()
        {
            this._builder.BuildPartA();
        }
		
        public void buildFullFeaturedProduct()
        {
            this._builder.BuildPartA();
            this._builder.BuildPartB();
            this._builder.BuildPartC();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            // The client code creates a builder object, passes it to the
            // director and then initiates the construction process. The end
            // result is retrieved from the builder object.
            var director = new Director();
            var builder = new ConcreteBuilder();
            director.Builder = builder;
            
            Console.WriteLine("Standard basic product:");
            director.buildMinimalViableProduct();
            Console.WriteLine(builder.GetProduct().ListParts());

            Console.WriteLine("Standard full featured product:");
            director.buildFullFeaturedProduct();
            Console.WriteLine(builder.GetProduct().ListParts());

            // Remember, the Builder pattern can be used without a Director
            // class.
            Console.WriteLine("Custom product:");
            builder.BuildPartA();
            builder.BuildPartC();
            Console.Write(builder.GetProduct().ListParts());
        }
    }
}

Output.txt: Resultado de la ejecución

Standard basic product:
Product parts: PartA1

Standard full featured product:
Product parts: PartA1, PartB1, PartC1

Custom product:
Product parts: PartA1, PartC1

Builder en otros lenguajes

Patrones de diseño: Builder en Java Patrones de diseño: Builder en C++ Patrones de diseño: Builder en PHP Patrones de diseño: Builder en Python Patrones de diseño: Builder en Ruby Patrones de diseño: Builder en Swift Patrones de diseño: Builder en TypeScript Patrones de diseño: Builder en Go