建造者模式(Builder)

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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()); } }}

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Standard basic product:Product parts: PartA1Standard full featured product:Product parts: PartA1, PartB1, PartC1Custom product:Product parts: PartA1, PartC1