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classkotlinreflectioninstanceof

kotlin.reflect.KClass.isInstance(value: Any?) not working

I'm trying the follow

"simple string"::class.isInstance(kotlin.String)

But it return false!

I'm using

"org.jetbrains.kotlin:kotlin-reflect:1.3.21"

The another examples also fail

1::class.isInstance(kotlin.Int)
true::class.isInstance(Boolean)

Please, help me to understand it!

Solution

  • You use the API incorrectly, the isInstance function does the opposite check as shown in the documentation:

    Returns true if [value] is an instance of this class on a given platform.

    The kotlin.Int line does not refer to a type, you miss the ::class.

    A possible solution is to flip the declaration:

    String::class.isInstance("a string")  /// true
Int::class.isInstance(42) /// true

    You may also compare KClass objects, e.g. 432::class == Int::class or use KClass functions isSubclassOf and isSuperclassOf