带有嵌套对象的构建器模式 [英] Builder pattern with nested objects

问题描述

我遇到了一个问题.

我想实现构建器模式，以便更轻松地创建对象.我面临的问题与嵌套对象有关.我想创建的对象有一个其他对象的列表，我真的不知道如何解决它.

I want to implement the builder pattern to make creating my objects easier. The problem I face has to do with nested object. The object I would like to create has a list of other objects in it, and I don't really have an idea on how to tackle it.

我希望能够执行以下操作(例如更简单的对象):

I want to be able to do the following (Simpler objects for example):

Receipt RestaurantReceipt = new ReceiptBuilder()
.withDate("value")
.withName("value")
.AddItem("value")
    .WithIngredients("value")
    .WithType("value")
.AddItem("value")
    .WithIngredients("value")
    .WithType("value")
.build();

或者类似的东西:

Receipt RestaurantReceipt = new ReceiptBuilder()
.withDate("value")
.withName("value")
.AddItem("value", item => {
  .WithIngredients("value")
  .WithType("value")
})
.AddItem("value", item => {
  .WithIngredients("value")
  .WithType("value")
})
.build();

示例应该代表我的情况，尽管如果有不止一种类型的嵌套对象.

Example should be representative for my situation, although if got more than one type of nested object.

推荐答案

给定这样的代码

var rb = new ReceiptBuilder();
var receipt = rb.WithName("Name")
            .WithDate(DateTime.Now)
            .WithItem("Item1", i => i.WithIngredients("Ingredients1"))
            .WithItem("Item2", i => i.WithIngredients("Ingredients1"))
            .Build();
Console.WriteLine(receipt);

您的构建器非常简单，利用 WithItem 构建器方法中的一些简单谓词，允许消费者以与顶级 ReceiptBuilder 类似的构建器"模式配置每个项目:

Your builder is pretty simple, making use of some simple predicates inside the WithItem builder method to allow the consumer to configure each item in a similar "builder" pattern to the top level ReceiptBuilder:

public class ReceiptBuilder
{
    private Receipt r;

    public ReceiptBuilder()
    {
        r = new Receipt();
    }

    public ReceiptBuilder WithName(string name)
    {
        r.Name = name;
        return this;
    }

    public ReceiptBuilder WithDate(DateTime dt)
    {
        r.Date = dt;
        return this;
    }

    public ReceiptBuilder WithItem(string text, Action<ReceiptItemBuilder> itemBuilder)
    {
        var rib = new ReceiptItemBuilder(text);
        itemBuilder(rib);
        r.AddItem(rib.Build());
        return this;
    }

    public Receipt Build()
    {
        return r;
    }
}

public class ReceiptItemBuilder
{
    private ReceiptItem ri;

    public ReceiptItemBuilder(string text)
    {
        ri = new ReceiptItem(text);
    }

    public ReceiptItemBuilder WithIngredients(string ings)
    {
        ri.Ingredients = ings;
        return this;
    }

    // WithType omitted for brevity. 

    internal ReceiptItem Build()
    {
        return ri;
    }
}

工作示例:http://rextester.com/IRR50897

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