How to use scala classOf, typeOf, object

This article introduces the relevant knowledge of "how to use scala classOf, typeOf, object". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

In java, jvm uses type wipe at run time, and types can no longer be distinguished simply by class. For example, the class of List and List is Class, but the two types (type) are different.

In Scala, the type system is much more complex than java, which provides a scala.reflect.runtime.universe.Type of its own.

Use typeOf to get type information in scala:

Scala > import scala.reflect.runtime.universe._

Scala > class A

Scala > typeOf [A]

Res44: reflect.runtime.universe.Type = A

Similarly, it is also convenient to get Class information in scala:

Scala > classOf [A]

In addition, because the getClass method is provided in java's Object, for scala objects, you can also use the

Scala > val a = new A

Scala > a.getClass

Res53: Class [_ object O

Scala > classOf [O] / / where O is a singleton object and an instance

: 14: error: not found: type O

For an instance, the only way to get its Class information is through the getClass method

Scala > O.getClass

Res60: Class [_ class A {class B} / / nested classes

Scala > val A1 = new A

Scala > val a2 = new A

Scala > val b1 = new a1.B

Scala > val b2 = new a2.B

For instances of inner class B, their class are all the same: inner class B (indicating that B is the inner class of A)

Scala > b1.getClass

Res8: Class [_ b1.getClass = = b2.getClass

Res7: Boolean = true

But their types are different:

Scala > typeOf [a1.B] = = typeOf [a2.B]

Res10: Boolean = false

This is because internal types depend on external instances (path dependent types), and external instances are different from each other.

But you can also abstract this type again.

Scala > typeOf [a1.B] typeOf [a2.B] classOf [list [string]] = = classOf [list [string]] (type erase)

Res16: Boolean = true

Scala > typeOf [list [Int]] = = typeOf [list [string]]

Res17: Boolean = false

In jvm, instances of a class are in the form of references, while types do not have this constraint, and the underlying type int,byte,char and so on are non-referenced. Types are more "specific" and "more detailed" than classes.

This is the end of "how to use scala classOf, typeOf, object". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!