工厂模式，避免不同接口使用相同的开关盒 [英] Factory pattern, Avoid same switch case for different interface

问题描述

我有一个实现3个不同接口的模型

I have a Model which Implements 3 different interfaces

public class CustomerRateSettingModel :  IBaseFactory, IHandleSearch, IHandleSearchAggregate

我对实现设计模式并尝试实现Factory模式来创建实例非常陌生.但是我无法找到一种适当的方法来避免在编写Factory时使用相同的Switch语句

I am very new with implementing design patterns and trying to implement Factory pattern to create instances. But I am unable to find a proper way to avoid the identical Switch statements while writing Factory

  public static IHandleSearch GetClassInstanceForSearch(string className)
    {
        switch (className.ToLower())
        {
            case "customerratesettingmodel":
                return new CustomerRateSettingModel();

            default: return null;
        }
    }

    private static IBaseFactory ManufactureModel(string className)
    {
        switch (className.ToLower())
        {
            case "customerratesettingmodel":
                return new CustomerRateSettingModel();

            default: return null;
        }
    }

是否有正确的方法来处理类似情况?

Is there is any right way to handle scenarios like that?

供参考:调用工厂的代码

For Reference : the code calling the factory

  IHandleSearch instance = ModelFactory.GetClassInstanceForSearch(modelName);


 var modelResult = instance.GetSearch(indexName, searchHistory.SearchParameters);

推荐答案

制作一个 Dictionary< string，Func< object>> 以将名称映射到对象制造者.使用 as 运算符测试 object 是否符合所需的接口:

Make a Dictionary<string,Func<object>> to map names to object makers. Use as operator to test object for compliance with the desired interface:

static readonly IDictionary<string,Func<object>> Makers = new Dictionary<string,Func<object>> {
    ["customerratesettingmodel"] = () => new CustomerRateSettingModel()
};
public static IHandleSearch GetClassInstanceForSearch(string className) {
    return Construct<IHandleSearch>(className);
}
public static IBaseFactory GetClassInstanceForSearch(string className) {
    return Construct<IBaseFactory>(className);
}
private static T Construct<T>(string className) where T : class {
    if (!Makers.TryGetValue(className.ToLower(), out var makeObject) {
        return null;
    }
    return makeObject() as T;
}

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