具有类型约束或基类参数的泛型方法 [英] Generic method with type constraints or base class parameter

问题描述

据我所知，如果我编写一个接受从BaseClass(或接口)派生的参数的方法，则有两种方法可以实现:

If I write a method accepting a parameter which derives from a BaseClass (or an interface), as far as I know there are two ways to achieve that:

void MyMethod<T>(T obj) where T : BaseClass { ... }

和

void MyMethod(BaseClass obj) { ... }

使用一个相对于另一个有什么优点/缺点?

What advantages / disadvantages has using the one over the other?

推荐答案

在此示例中，两者之间没有太大区别，您可以访问方法中的相同成员，并且可以使用相同的派生类进行调用.在运行时会有所不同，因为针对每种类型调用的泛型方法都会被编译.

In this example there isn't a big difference between the two, you can access the same members inside the method and you can call it with the same derived classes. There is a runtime difference as a generic method is compiled for each type it is invoked with.

泛型有用的地方是如果您根据T

Where generics come in useful would be if you would return a value depending on T

使用泛型，您可以执行以下操作

With generics you could do the following

T MyMethod<T>(T obj) where T : BaseClass { ... }
MyMethod(derivedInstance).derivedProperty

没有这将是一个错误:

BaseClass MyMethod(BaseClass obj) { ... }
MyMethod(derivedInstance).derivedProperty // error

注意尽管您提到了约束基类，但值得一提的是，如果您约束的不是基类，而是接口，则通过结构中的结构实现额外的装箱操作.非通用版本，这可能会对性能产生严重影响.

Note Although you mention constraining to a base class, it is worth mentioning that if you constrain not to a class, but to an interface, extra boxing will occur if the implementation is by a struct in the non generic version, this can have severe performance implications.

这篇关于具有类型约束或基类参数的泛型方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！