工厂模式，避免不同接口使用相同的switch case

Question

我有一个实现了 3 个不同接口的模型

public class CustomerRateSettingModel :  IBaseFactory, IHandleSearch, IHandleSearchAggregate

我对实施设计模式和尝试实施工厂模式来创建实例非常陌生。但是我在编写 Factory

时找不到避免相同 Switch 语句的正确方法

  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;
        }
    }

有什么正确的方法来处理这样的场景吗？

供参考：调用工厂的代码

  IHandleSearch instance = ModelFactory.GetClassInstanceForSearch(modelName);


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

Answer 1

创建一个 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：

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;
}

工厂模式，避免不同接口使用相同的switch case

Factory pattern, Avoid same switch case for different interface

c#

design-patterns

interface

factory-pattern