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我在我的应用程序的一个部分中使用工厂设计模式,我注意到使用常规工厂模式每次都会创建一个新对象。我有一个场景,我需要多次迭代工厂类中的 createinstance 方法,并且每次创建新的消费者对象时。
在 Program.cs 中,我创建了人员列表,我在其中键入了一些随机输入数据。基于对每个人的操作的代码应该动态地执行该类中的 process 方法。这个逻辑似乎像我预期的那样工作,但是如果重复相同的操作,那么会多次创建相同的对象。
为了解决这个问题,我修改了 ActionFactory 类(如下面的 Modified Action Factory 片段所示),我在其中维护一个字典来保存为特定操作创建的实例。如果重复该操作,则不是创建新实例,而是从字典中获取先前创建的实例。这似乎已经解决了问题,如 Output2 图像所示。
但是我想知道/向专业人士学习,如果我在“Modified Action Factory”类中所做的工作是否足够(或者)对于这类问题我应该使用其他模式而不是工厂设计模式。为了维护单个对象,我能想到的另一种方法可能是在每个 Action 类中创建一个单例对象,但问题是如何从工厂类调用单例实例?因为工厂类总是调用 createinstance 而不会调用单例实例..我是设计模式的新手,我正在努力学习更多关于它们的知识并提高我的编码标准。提前致谢
下面是代码:
class Program
{
static void Main(string[] args)
{
List<Person> ListofPeople = new List<Person>();
Person p1 = new Person() {Name = "P1", State = "CA", Action = "Add"};
ListofPeople.Add(p1);
Person p2 = new Person() { Name = "P2", State = "NJ", Action = "Add" };
ListofPeople.Add(p2);
Person p3 = new Person() { Name = "P3", State = "VA", Action = "Update" };
ListofPeople.Add(p3);
Person p4 = new Person() { Name = "P4", State = "VA", Action = "Update" };
ListofPeople.Add(p4);
Person p5 = new Person() { Name = "P5", State = "VA", Action = "Update" };
ListofPeople.Add(p5);
Person p6 = new Person() { Name = "P6", State = "VA", Action = "Delete" };
ListofPeople.Add(p6);
ActionFactory factory= new ActionFactory();
foreach (var person in ListofPeople)
{
IAction action = (IAction) factory.CreateInstance(person.Action.ToLower());
action.Process();
}
Console.ReadKey();
}
}
public class Person
{
public string Name { get; set; }
public string State { get; set; }
public string Action { get; set; }
}
Action 工厂:
public class ActionFactory
{
Dictionary<string, Type> actions;
public ActionFactory()
{
LoadTypesICanReturn();
}
public object CreateInstance(string actionName)
{
Type t = GetTypeToCreate(actionName);
if (t == null)
return null;
var actionProcessor = Activator.CreateInstance(t) as IAction;
return actionProcessor;
}
Type GetTypeToCreate(string actionName)
{
foreach (var action in actions)
{
if (action.Key.Contains(actionName))
{
return actions[action.Key];
}
}
return null;
}
void LoadTypesICanReturn()
{
actions = new Dictionary<string, Type>();
Type[] typesInThisAssembly = Assembly.GetExecutingAssembly().GetTypes();
foreach (Type type in typesInThisAssembly)
{
if (type.GetInterface(typeof(IAction).ToString()) != null)
{
actions.Add(type.Name.ToLower(), type);
}
}
}
}
Action :
public interface IAction
{
void Process();
}
添加.cs
public class Add: IAction
{
public Add()
{
Console.WriteLine("add constructor...");
}
#region IAction Members
public void Process()
{
Console.WriteLine("Add Processor....");
}
#endregion
}
更新.cs
public class Update: IAction
{
public Update()
{
Console.WriteLine("Update constructor...");
}
public void Process()
{
Console.WriteLine("Update Processor...");
}
}
删除.cs
public class Delete : IAction
{
public Delete()
{
Console.WriteLine("Delete Constructor...");
}
#region IAction Members
public void Process()
{
Console.WriteLine("Delete Processor...");
}
#endregion
}
控制台输出显示 IAction 消费者类被实例化的次数
输出:
修改后的 Action 工厂:
public class ActionFactory
{
Dictionary<string, Type> actions;
private Dictionary<Type, IAction> actionInstances;
public ActionFactory()
{
actionInstances = new Dictionary<Type, IAction>();
LoadTypesICanReturn();
}
public object CreateInstance(string actionName)
{
Type t = GetTypeToCreate(actionName);
if (t == null)
return null;
if (actionInstances.ContainsKey(t))
return actionInstances[t];
else
{
var actionProcessor = Activator.CreateInstance(t) as IAction;
LoadIAction(t, actionProcessor);
return actionProcessor;
}
}
private void LoadIAction(Type t, IAction actionProcessor)
{
if (!actionInstances.ContainsKey(t))
{
actionInstances.Add(t, actionProcessor);
}
}
Type GetTypeToCreate(string actionName)
{
foreach (var action in actions)
{
if (action.Key.Contains(actionName))
{
return actions[action.Key];
}
}
return null;
}
void LoadTypesICanReturn()
{
actions = new Dictionary<string, Type>();
Type[] typesInThisAssembly = Assembly.GetExecutingAssembly().GetTypes();
foreach (Type type in typesInThisAssembly)
{
if (type.GetInterface(typeof(IAction).ToString()) != null)
{
actions.Add(type.Name.ToLower(), type);
}
}
}
}
带有修改的 Action 工厂的输出:
最佳答案
Factory
设计模式用于简化对象的创建,通常当您不知道要创建的类型时,它将在运行时提供。
有时,也可能是因为它们有依赖关系,而你想抽象依赖关系的创建,或者只是因为你想做一些事情。
在您的情况下,Add
, Update
, 和 Delete
是通常由某些第 3 方调用的方法,而不是数据类型本身,由 @sokohavi
指定多于。
您的案件可以由Command Design Pattern
处理.
假设你想加载一堆命令(又名:Add Person X, Update Person Y, Delete Person Z
),并且你想缓冲它们以备将来使用。
abstract class PersonCommand
{
Person Person { protected get; } // you can call this payload, or person, w/e
PersonCommand(Person person)
{
Person = person;
}
public abstract void Apply(); // can be called Execute or Process as well, or w/e. problem domain.
}
然后,每个命令都有一个实现:
class AddCommand : PersonCommand
{
AddCommand(Person person) : base(person) { }
public override void Apply()
{
// send REST PUT request, add person to DB, whatever you want to do here.
}
}
class UpdateCommand : PersonCommand
{
UpdateCommand(Person person) : base(person) { }
public override void Apply()
{
// send REST POST request, update person in DB, whatever you want to do here.
}
}
class DeleteCommand : PersonCommand
{
DeleteCommand(Person person) : base(person) { }
public override void Apply()
{
// send REST DELETE request, remove person from DB, whatever you want to do here.
}
}
当你有这个时,你可以执行以下操作:
var commandsToExecute = new List<PersonCommand>();
commandsToExecute.Add(new AddCommand(new Person { Name = "asd", State = "CA" }));
commandsToExecute.Add(new UpdateCommand(new Person { Name = "barry", State = "CA" }));
commandsToExecute.Add(new DeleteCommand(new Person { Name = "barry", State = "CA" }));
commandsToExecute.ForEach(cmd => cmd.Apply());
现在,这是您可以做什么的基本示例。
也许,在某些情况下,
Command
s 不是那么容易创建的,例如,它们可能需要了解 REST 请求的服务端点。为此,一个
CommandFactory
可以创建,然后可以通过操作名称处理创建:class CommandFactory
{
private readonly Dictionary<string, Func<Person, PersonCommand>> creationFuncs;
CommandFactory(string backendUrl)
{
creationFuncs = new Dictionary<string, Func<Command, Person>>();
creationFuncs.Add("add", (person) => return new AddCommand(backendUrl, person));
creationFuncs.Add("update", (person) => return new UpdateCommand(backendUrl, person));
creationFuncs.Add("delete", (person) => return new DeleteCommand(backendUrl, person));
}
PersonCommand Create(string action, Person person)
{
// validation can be added here
return creationFuncs[action](person);
}
}
用法是:
var factory = new CommandFactory("http://localhost:4200/person/");
var commandsToExecute = new List<PersonCommand>();
commandsToExecute.Add(factory.Create("add", new Person { Name = "asd", State = "CA" }));
commandsToExecute.Add(factory.Create("update", new Person { Name = "barry", State = "CA" }));
commandsToExecute.Add(factory.Create("delete", new Person { Name = "barry", State = "CA" }));
commandsToExecute.ForEach(cmd => cmd.Apply());
任何事物都有设计模式,您应该只找到适合您需要的设计模式。
关于c# - 工厂模式和对象持久性,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43310187/