在 Kotlin 中，：：class.simpleName是做什么的

• In Kotlin, the ::class operator exists in 2 forms:
  • TypeName::class - which returns a KClass object for the static type TypeName.
  • variableName::class-which returns a KClass object corresponding to the runtime type/variableName，以及not-variableName的静态类型.(Kotlin在他们的文档中称之为"绑定类型").
• 在您的例子中，var1的运行时tytpe为String，但静态类型为Any.
• 但是，与大多数静态类型语言一样，Kotlin的类型系统不允许隐式缩小转换(即，给定一个类型为String的变量var2，您不能从另一个静态类型为Any的变量(var3)分配给var2，因为var3 could的运行时类型与String完全不兼容，例如InputStream对象.

In context:

fun main() {

    val var1: Any = "Carmelo Anthony"
    val var1Type = var1::class.simpleName
    println("var1's type: " + var1Type) // <-- This will print the *runtime type* of `var1` (String), not its static type (which is `Any`, *not* `String`).

    /*
    val var2: String = var1 // <-- Fails beause `var1` is `Any`, and `Any` is "wider" than `String`, and narrowing conversions always considered unsafe in languages like Kotlin, Java, etc.
    */
    val var2Unsafe: String  = var1 as  String; // <-- Doing this is unsafe because it will throw if `var1` is not a String.
    val var2Safe  : String? = var1 as? String; // <-- Doing this is safe because it `var2Safe` will be null if `var1` is not a String.
    
    println(var2Unsafe)
    println(var2Safe)
}

如果您熟悉其他语言，那么下面是一个不完整的等效操作及其语法表: