如何在泛型中使用工厂模式
本文关键字:工厂 模式 泛型 | 更新日期: 2023-09-27 17:54:45
我希望创建一个PresenterFactory,它显然负责创建演示器实例。
根据本题提供的代码示例:
如何Moq这个视图?
和@Pacane的回答,我想我会这样写:
PresenterFactoryTests
[TestClass]
public class PresenterFactoryTests {
[TestClass]
public class Instance : PresenterFactoryTests {
[TestMethod]
public void ReturnsInstantialized() {
// arrange
Type expected = typeof(PresenterFactory);
// act
PresenterFactory actual = PresenterFactory.Instance;
// assert
Assert.IsNotNull(actual);
Assert.IsInstanceOfType(actual, expected);
}
[TestMethod]
public void ReturnsSame() {
// arrange
PresenterFactory expected = PresenterFactory.Instance;
// act
PresenterFactory actual = PresenterFactory.Instance;
// assert
Assert.AreSame(expected, actual);
}
}
[TestClass]
public class Create : PresenterFactoryTests {
[TestMethod]
public void ReturnsAuthenticationPresenter {
// arrange
Type expected = typeof(IAuthenticationPresenter);
// act
IAuthenticationPresenter actual =
PresenterFactory
.Instance
.Create<IAuthenticationPresenter, IAuthenticationView>(
new MembershipService());
// assert
Assert.IsInstanceOfType(actual, expected);
}
// Other tests here...
}
}
PresenterFactory
public sealed PresenterFactory {
private PresenterFactory() { }
public static PresenterFactory Instance { get { return getInstance(); } }
P Create<P, V>(params object[] args) where P : IPresenter<V> where V : IView {
V view = (V)Activator.CreateInstance<V>();
return Activator.CreateInstance(typeof(P), view, args);
}
private static PresenterFactory getInstance() {
if (instance == null) instance = new PresenterFactory();
return instance;
}
private static PersenterFactory instance;
}
ApplicationPresenter
public class ApplicationPresenter : Presenter<IApplicationView>, IApplicationPresenter {
public ApplicationPresenter(IApplicationView view, PresenterFactory presenters)
: base (view) {
Presenters = presenters;
// other initializing stuff here...
}
}
然而,由于类型的限制,我似乎无法做到上述测试中所述的。
在我的PresenterFactoryTests.Create.ReturnsAuthenticationPresenter
测试方法中,当我使用接口作为类型参数时,它在运行时编译并抛出,因为Activator.CreateInstance
不能创建接口的实例。
PresenterFactory
是ApplicationPresenter
所需要的,我将通过它的构造函数注入它,以便应用程序可以实例化所有可用的呈现者,这取决于用户所要求的特性。
我错过了什么?
我认为你需要一个更通用的参数-具体类型的视图,因为你需要两个具体的类型(视图和演示器能够创建它们)和视图的接口类型:
P Create<P, V, IV>(params object[] args)
where P : IPresenter<V> where V :IV, IV: IView {