做网站的前端是做什么,哪个网站可以免费建站,自用电脑做网站,青岛网站推广公司本篇纯属抬杠之作#xff0c;之前我们提到了Swift的泛型Protocol使用associatedtype关键字#xff0c;而不是使用Type语法的泛型参数。这其中有什么好处呢#xff1f; 我就这个问题搜索了一些回答#xff0c;大体上提到两点#xff1a; Type语法对Protoco… 本篇纯属抬杠之作之前我们提到了Swift的泛型Protocol使用associatedtype关键字而不是使用Type语法的泛型参数。这其中有什么好处呢 我就这个问题搜索了一些回答大体上提到两点 Type语法对Protocol没有意义Protocol仅需要定义一个抽象的概念具体的类型应该由实现的Class来明确比如 ClassWithIntInt: NumberProtocol
ClassWithDoubleDouble: NumberProtocolassociatedtype可以用来给Protocol中特定Func添加泛型约束而不是限定整个Protocol protocol GeneratorType {associatedtype Elementpublic mutating func next() - Self.Element?
}听上去还是有一定道理的然后实践是检验事实的唯一标准。下面我们通过代码实例来和C#进行对比。首先拿出网上多被引用解释上述两个观点的Swift代码 public protocol Automobile {associatedtype FuelTypeassociatedtype ExhaustTypefunc drive(fuel: FuelType) - ExhaustType
}
public protocol Fuel {associatedtype ExhaustTypefunc consume() - ExhaustType
}
public protocol Exhaust {init()func emit()
}public struct UnleadedGasolineE: Exhaust: Fuel {public func consume() - E {print(...consuming unleaded gas...)return E()}
}
public struct CleanExhaust: Exhaust {public init() {}public func emit() {print(...this is some clean exhaust...)}
}
public class CarF: Fuel,E: Exhaust: Automobile where F.ExhaustType E {public func drive(fuel: F) - E {return fuel.consume()}
}public class Car1F: Fuel: Automobile {public func drive(fuel: F) - F.ExhaustType {return fuel.consume()}
}具体的使用情况如下 var car CarUnleadedGasolineCleanExhaust, CleanExhaust()
car.drive(fuel: UnleadedGasolineCleanExhaust()).emit()var fusion Car1UnleadedGasolineCleanExhaust()
fusion.drive(fuel: UnleadedGasolineCleanExhaust()).emit()转换成C#代码的话有两种思路首先是把泛型参数放到Interface层面 public interface AutomobileFuelType, ExhaustType{ExhaustType Drive(FuelType fuel);}public interface FuelExhaustType{ExhaustType consume();}public interface Exhaust {void Emit();}public class UnleadedGasolineExhaust : FuelExhaust where Exhaust : new(){public Exhaust consume(){Console.WriteLine(...consuming unleaded gas...);return new Exhaust();}}public class CleanExhaust : Exhaust{public void Emit(){Console.WriteLine(...this is some clean exhaust...);}}public class Car : AutomobileUnleadedGasolineCleanExhaust, CleanExhaust{public CleanExhaust Drive(UnleadedGasolineCleanExhaust fuel){return fuel.consume();}} 还可以模仿Swift对Automobile多做一层继承进行包装 public interface Car1T1 : AutomobileUnleadedGasolineT1, T1 where T1 : new(){}public class SimpleCar : Car1CleanExhaust{public CleanExhaust Drive(UnleadedGasolineCleanExhaust fuel){return fuel.consume();}} 调用的时候没有什么太大的差别 var gaso new UnleadedGasolineCleanExhaust();var car new Car();car.Drive(gaso).Emit(); var simpleCar new SimpleCar();simpleCar.Drive(gaso).Emit(); 和Swift比较不同的是我们在Interface就代入了泛型参数。但是由于我们不能直接实例化Interface所以并不能直接使用Automobile来减少一层继承关系。 因为上述提到的使用associatedtype 的第一点理由见仁见智这里不分高下。 C#还有第二种思路就是我也把泛型约束下放到Func层级 public interface Automobile{ExhaustType DriveFuelType,ExhaustType(FuelType fuel) where ExhaustType : new();}public interface Fuel{ExhaustType consumeExhaustType() where ExhaustType : new();}public class UnleadedGasoline : Fuel{public Exhaust consumeExhaust() where Exhaust : new(){Console.WriteLine(...consuming unleaded gas...);return new Exhaust();}}public class Car2 : Automobile{public CleanExhaust DriveUnleadedGasoline, CleanExhaust(UnleadedGasoline fuel) where CleanExhaust : new(){return (fuel as Fuel).consumeCleanExhaust();}} C#的接口并不能定义构造函数。强行模仿起来还真是有点累啊。最终的使用也很简单 var fuel new UnleadedGasoline();var car2 new Car2();car2.DriveUnleadedGasoline,CleanExhaust(fuel).Emit(); 通篇比较下来应该说Swift通过associatedtype 关键字和Type的混用使得泛型的定义更为复杂也更灵活了。 GitHub https://github.com/manupstairs/LearnSwift https://github.com/manupstairs/LearnDotNetCore 转载于:https://www.cnblogs.com/manupstairs/p/5980850.html
