
C# 生成器模式讲解和代码示例
生成器是一种创建型设计模式, 使你能够分步骤创建复杂对象。
与其他创建型模式不同, 生成器不要求产品拥有通用接口。 这使得用相同的创建过程生成不同的产品成为可能。
复杂度:
流行度:
使用示例: 生成器模式是 C# 世界中的一个著名模式。 当你需要创建一个可能有许多配置选项的对象时, 该模式会特别有用。
识别方法: 生成器模式可以通过类来识别, 它拥有一个构建方法和多个配置结果对象的方法。 生成器方法通常支持方法链 (例如 someBuilder.setValueA(1).setValueB(2).create()
)。
概念示例
本例说明了生成器设计模式的结构并重点回答了下面的问题:
- 它由哪些类组成?
- 这些类扮演了哪些角色?
- 模式中的各个元素会以何种方式相互关联?
Program.cs: 概念示例
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: 执行结果
Standard basic product: Product parts: PartA1 Standard full featured product: Product parts: PartA1, PartB1, PartC1 Custom product: Product parts: PartA1, PartC1