我正在尝试用 C# 创建一个非常简单的工厂类。唯一的障碍是我需要传递一个参数。
这是我要创建的类:
public class ClassToCreate
{
private readonly string myValue;
public ClassToCreate(string myValue)
{
this.myValue = myValue;
}
}
首先我打算像这样创建工厂方法
public T CreateNewClass<T>(string value) where T : class, new()
但是你不能传递参数 - 所以我试过了
public class FactoryClass
{
private object _instance = null;
public T CreateNewClass<T>(Func<string, T> createWithValue) where T : class
{
if (_instance == null)
_instance = createWithValue(??string here??);
return (T)_instance;
}
}
调用它的类
string somestring = "hello world";
var factory = new FactoryClass();
var myclass = factory.CreateNewClass<ClassToCreate>(_ => new ClassToCreate(somestring));
理想情况下,上面的调用代码只会传递值 - 但我无法让它接受任何东西...
最佳答案
尝试创建工厂类的另一种方法是创建一个更抽象的版本,它允许您在运行时定义工厂并将工厂组件与实例化实例的代码分开。
所以,这种工厂可以这样使用:
var factory = new AbstractFactoryClass();
factory.Register<string, ClassToCreate>(p => new ClassToCreate(p));
factory.Register<string, int, Person>((name, age) => new Person(name, age));
然后,稍后在您的代码中,您可以编写此代码来实际实例化您的实例:
var instance = factory.Create<string, ClassToCreate>("Hello");
var person = factory.Create<string, int, Person>("Fred", 99);
这是你需要的类:
public class AbstractFactoryClass
{
private Dictionary<Type, Delegate> _factories = new();
public void Register<T>(Func<T> factory) => _factories[typeof(Func<T>)] = factory;
public void Register<P, T>(Func<P, T> factory) => _factories[typeof(Func<P, T>)] = factory;
public void Register<P1, P2, T>(Func<P1, P2, T> factory) => _factories[typeof(Func<P1, P2, T>)] = factory;
public void Register<P1, P2, P3, T>(Func<P1, P2, P3, T> factory) => _factories[typeof(Func<P1, P2, P3, T>)] = factory;
public T Create<T>() => ((Func<T>)_factories[typeof(Func<T>)])();
public T Create<P, T>(P p) => ((Func<P, T>)_factories[typeof(Func<P, T>)])(p);
public T Create<P1, P2, T>(P1 p1, P2 p2) => ((Func<P1, P2, T>)_factories[typeof(Func<P1, P2, T>)])(p1, p2);
public T Create<P1, P2, P3, T>(P1 p1, P2 p2, P3 p3) => ((Func<P1, P2, P3, T>)_factories[typeof(Func<P1, P2, P3, T>)])(p1, p2, p3);
}
public class ClassToCreate
{
private readonly string myValue;
public ClassToCreate(string myValue)
{
this.myValue = myValue;
}
public override string ToString() => myValue;
}
public class Person
{
private readonly string name;
private readonly int age;
public Person(string name, int age)
{
this.name = name;
this.age = age;
}
public override string ToString() => $"{name} is {age} years old";
}
现在,您可以用它来实例化接口(interface),因为这非常酷。
试试这段代码:
public interface IFoo
{
string Name { get; }
}
public class Foo1 : IFoo
{
private readonly string name;
public Foo1(string name)
{
this.name = name;
}
public string Name => name;
}
public class Foo2 : IFoo
{
private readonly string name;
public Foo2(string name)
{
this.name = name;
}
public string Name => name;
}
现在我可以像这样注册和创建接口(interface)了:
// during set up
factory.Register<string, IFoo>(n => new Foo1(n));
// somewhere later in my code:
IFoo foo = factory.Create<string, IFoo>("Fred");
我现在可以轻松地将我的 Register
调用更改为 n => new Foo2(n)
以及稍后调用 Create
方法的代码没有改变。它刚刚得到一个 Foo2
。
您可以轻松交换不同的存储库 - 从文件或数据库中读取 - 或向界面添加装饰器。
让我们试试这些类:
public interface IBar
{
string Name { get; }
}
public class BarCore : IBar
{
public string Name { get; private set; }
public BarCore(string name)
{
this.Name = name;
}
}
public class BarDecorator : IBar
{
private IBar _bar;
public BarDecorator(IBar bar)
{
this._bar = bar;
}
public string Name
{
get
{
Console.WriteLine($"You called Name on {_bar.GetType().Name}");
return _bar.Name;
}
}
}
我可以这样运行:
// during set up
factory.Register<string, IBar>(n => new BarCore(n));
// somewhere later in my code:
IBar bar = factory.Create<string, IBar>("Fred");
Console.WriteLine($"{bar.Name} from {bar.GetType().Name}");
我得到这个输出:
Fred from BarCore
但是,如果我将我的注册码更改为:
factory.Register<string, IBar>(n => new BarDecorator(new BarCore(n)));
我不需要更改我的后续代码,但是当我运行它时,我现在得到这个:
You called Name on BarCore
Fred from BarDecorator
即时调试!
关于c# - 使用参数在 C# 中创建通用工厂,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/71630469/