如何写出最优美的工厂模式

提问

如何写出最优美的工厂模式

回答

首先定义什么是最优美
最优美代表着他：面对新增开放，面对修改关闭实践
那么如何实现呢？
我选择使用特性 + 反射

 public ICommand? BuildCommand(string[]? args)
        {
            if (args == null || args.Length != 2)
                throw new ArgumentException("请输入正确的命令和参数");
            ICommand? command = null;
            
            var assembly = Assembly.GetExecutingAssembly();
            if (!Equals(null, assembly))
            {
                var typeInfos = assembly.DefinedTypes.Where(t =>
                    t.CustomAttributes.Select(r => r.AttributeType).ToList().Contains(typeof(CommandAttribute)));
                var typeInfo = typeInfos.FirstOrDefault(r => r.GetCustomAttributes(typeof(CommandAttribute)).Any(w => ((w as CommandAttribute)!).Name.Equals(args[0])));//.GetCustomAttribute(typeof(CommandAttribute)) as CommandAttribute;
                if (!Equals(typeInfo, null))
                {
                    if (typeInfo.FullName != null)
                    {
                        var serviceProvider = ServiceProviderHelper.GetInstance().ServiceProvider;
                        if (serviceProvider != null)
                            command = assembly.CreateInstance(typeInfo.FullName, true, BindingFlags.Default, null,
                                new object[]
                                {
                                    args[1],
                                    serviceProvider.GetService<IQualityControl>() ??
                                    throw new InvalidOperationException()
                                }, null, null) as ICommand;
                    }
                }

            }
            return command;
        }

定义的特性

[AttributeUsage(AttributeTargets.Class)]
    public class CommandAttribute : Attribute
    {
        public string Name { get; set; }

        public CommandAttribute(string name)
        {
            Name = name;
        }
    }