我正在寻找一个如何实现工厂类的简单示例,但不使用Switch或If-Then语句。我可以找到的所有示例都使用一个。例如,如何修改此简单示例(如下),以使实际工厂不依赖于Switch?在我看来,该示例违反了打开/关闭原则。我希望能够添加具体的类(“经理”,“文员”,“程序员”等),而无需修改工厂类。
谢谢!
class Program
{
abstract class Position
{
public abstract string Title { get; }
}
class Manager : Position
{
public override string Title
{
get { return "Manager"; }
}
}
class Clerk : Position
{
public override string Title
{
get { return "Clerk"; }
}
}
class Programmer : Position
{
public override string Title
{
get { return "Programmer"; }
}
}
static class Factory
{
public static Position Get(int id)
{
switch (id)
{
case 0: return new Manager();
case 1: return new Clerk();
case 2: return new Programmer();
default: return new Programmer();
}
}
}
static void Main(string[] args)
{
for (int i = 0; i <= 2; i++)
{
var position = Factory.Get(i);
Console.WriteLine("Where id = {0}, position = {1} ", i, position.Title);
}
Console.ReadLine();
}
}
更新:
哇!谢谢大家!我学到了很多。收集了所有反馈后,我混合了一些答案并提出了答案。我愿意就更好的方法进行进一步的对话。
class Program
{
public interface IPosition
{
string Title { get; }
}
class Manager : IPosition
{
public string Title
{
get { return "Manager"; }
}
}
class Clerk : IPosition
{
public string Title
{
get { return "Clerk"; }
}
}
class Programmer : IPosition
{
public string Title
{
get { return "Programmer"; }
}
}
static class PositionFactory
{
public static T Create<T>() where T : IPosition, new()
{
return new T();
}
}
static void Main(string[] args)
{
IPosition position0 = PositionFactory.Create<Manager>();
Console.WriteLine("0: " + position0.Title);
IPosition position1 = PositionFactory.Create<Clerk>();
Console.WriteLine("1: " + position1.Title);
IPosition position2 = PositionFactory.Create<Programmer>();
Console.WriteLine("1: " + position2.Title);
Console.ReadLine();
}
}
另一个编辑:
也可以使用未知类型创建Interface的实例:
static class PositionFactory
{
public static IPosition Create(string positionName)
{
Type type = Type.GetType(positionName);
return (IPosition)Activator.CreateInstance(type);
}
}
然后可以这样称呼它:
IPosition position = PositionFactory.Create("Manager");
Console.WriteLine(position.Title);
最佳答案
怎么样(不需要字典,请注意,如果尝试Create<Position>()
,将会出现语法错误):
编辑-更新为使用显式实现的IPosition接口(interface)。只有IPosition实例可以访问成员函数(例如<implementation of Manager>.Title
将不会编译)。
编辑#2 Factory.Create应该在正确使用接口(interface)时返回IPosition而不是T。
using System;
using System.Collections.Generic;
class Program
{
interface IPosition
{
string Title { get; }
bool RequestVacation();
}
class Manager : IPosition
{
string IPosition.Title
{
get { return "Manager"; }
}
bool IPosition.RequestVacation()
{
return true;
}
}
class Clerk : IPosition
{
int m_VacationDaysRemaining = 1;
string IPosition.Title
{
get { return "Clerk"; }
}
bool IPosition.RequestVacation()
{
if (m_VacationDaysRemaining <= 0)
{
return false;
}
else
{
m_VacationDaysRemaining--;
return true;
}
}
}
class Programmer : IPosition
{
string IPosition.Title
{
get { return "Programmer"; }
}
bool IPosition.RequestVacation()
{
return false;
}
}
static class Factory
{
public static IPosition Create<T>() where T : IPosition, new ()
{
return new T();
}
}
static void Main(string[] args)
{
List<IPosition> positions = new List<IPosition>(3);
positions.Add(Factory.Create<Manager>());
positions.Add(Factory.Create<Clerk>());
positions.Add(Factory.Create<Programmer>());
foreach (IPosition p in positions) { Console.WriteLine(p.Title); }
Console.WriteLine();
Random rnd = new Random(0);
for (int i = 0; i < 10; i++)
{
int index = rnd.Next(3);
Console.WriteLine("Title: {0}, Request Granted: {1}", positions[index].Title, positions[index].RequestVacation());
}
Console.ReadLine();
}
}
关于c# - 没有开关或If/Then的工厂模式,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/33878216/