我熟悉这些模式,但仍然不知道如何处理以下情况:
public class CarFactory
{
public CarFactory(Dep1,Dep2,Dep3,Dep4,Dep5,Dep6)
{
}
public ICar CreateCar(type)
{
switch(type)
{
case A:
return new Car1(Dep1,Dep2,Dep3);
break;
case B:
return new Car2(Dep4,Dep5,Dep6);
break;
}
}
}
一般来说,问题在于需要注入(inject)的引用数量。车多了就更糟了。
我想到的第一个方法是在工厂构造函数中注入(inject) Car1 和 Car2,但它违反工厂方法,因为工厂将始终返回相同的对象。第二种方法是注入(inject) servicelocator 但它到处都是反模式。如何解决?
编辑:
备选方式1:
public class CarFactory
{
public CarFactory(IContainer container)
{
_container = container;
}
public ICar CreateCar(type)
{
switch(type)
{
case A:
return _container.Resolve<ICar1>();
break;
case B:
return _container.Resolve<ICar2>();
break;
}
}
}
替代方法2(由于树中的依赖太多而难以使用):
public class CarFactory
{
public CarFactory()
{
}
public ICar CreateCar(type)
{
switch(type)
{
case A:
return new Car1(new Dep1(),new Dep2(new Dep683(),new Dep684()),....)
break;
case B:
return new Car2(new Dep4(),new Dep5(new Dep777(),new Dep684()),....)
break;
}
}
}
最佳答案
在工厂内部使用 switch case 语句是一种代码味道。有趣的是,您似乎根本没有专注于解决该问题。
这种情况下最好、最友好的 DI 解决方案是 strategy pattern .它允许您的 DI 容器将依赖项注入(inject)到它们所属的工厂实例中,而不会用这些依赖项混淆其他类或求助于服务定位器。
接口(interface)
public interface ICarFactory
{
ICar CreateCar();
bool AppliesTo(Type type);
}
public interface ICarStrategy
{
ICar CreateCar(Type type);
}
工厂
public class Car1Factory : ICarFactory
{
private readonly IDep1 dep1;
private readonly IDep2 dep2;
private readonly IDep3 dep3;
public Car1Factory(IDep1 dep1, IDep2 dep2, IDep3 dep3)
{
this.dep1 = dep1 ?? throw new ArgumentNullException(nameof(dep1));
this.dep2 = dep2 ?? throw new ArgumentNullException(nameof(dep2));
this.dep3 = dep3 ?? throw new ArgumentNullException(nameof(dep3));
}
public ICar CreateCar()
{
return new Car1(this.dep1, this.dep2, this.dep3);
}
public bool AppliesTo(Type type)
{
return typeof(Car1).Equals(type);
}
}
public class Car2Factory : ICarFactory
{
private readonly IDep4 dep4;
private readonly IDep5 dep5;
private readonly IDep6 dep6;
public Car2Factory(IDep4 dep4, IDep5 dep5, IDep6 dep6)
{
this.dep4 = dep4 ?? throw new ArgumentNullException(nameof(dep4));
this.dep5 = dep5 ?? throw new ArgumentNullException(nameof(dep5));
this.dep6 = dep6 ?? throw new ArgumentNullException(nameof(dep6));
}
public ICar CreateCar()
{
return new Car2(this.dep4, this.dep5, this.dep6);
}
public bool AppliesTo(Type type)
{
return typeof(Car2).Equals(type);
}
}
策略
public class CarStrategy : ICarStrategy
{
private readonly ICarFactory[] carFactories;
public CarStrategy(ICarFactory[] carFactories)
{
this.carFactories = carFactories ?? throw new ArgumentNullException(nameof(carFactories));
}
public ICar CreateCar(Type type)
{
var carFactory = this.carFactories
.FirstOrDefault(factory => factory.AppliesTo(type));
if (carFactory == null)
{
throw new InvalidOperationException($"{type} not registered");
}
return carFactory.CreateCar();
}
}
用法
// I am showing this in code, but you would normally
// do this with your DI container in your composition
// root, and the instance would be created by injecting
// it somewhere.
var strategy = new CarStrategy(new ICarFactory[] {
new Car1Factory(dep1, dep2, dep3),
new Car2Factory(dep4, dep5, dep6)
});
// And then once it is injected, you would simply do this.
// Note that you could use a magic string or some other
// data type as the parameter if you prefer.
var car1 = strategy.CreateCar(typeof(Car1));
var car2 = strategy.CreateCar(typeof(Car2));
请注意,因为没有 switch case 语句,您可以在不更改设计的情况下向策略添加额外的工厂,并且每个工厂都可以有自己的依赖项,这些依赖项由 DI 容器注入(inject)。
var strategy = new CarStrategy(new ICarFactory[] {
new Car1Factory(dep1, dep2, dep3),
new Car2Factory(dep4, dep5, dep6),
new Car3Factory(dep7, dep8, dep9)
});
var car1 = strategy.CreateCar(typeof(Car1));
var car2 = strategy.CreateCar(typeof(Car2));
var car3 = strategy.CreateCar(typeof(Car3));
关于c# - 带有 DI 和 IoC 的工厂方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31950362/