Reified type parameters with inline in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the inline keyword do in Kotlin functions?

The inline keyword tells the compiler to copy the function's code directly where it is called, which can improve performance by avoiding function call overhead.

intermediate

What is a reified type parameter in Kotlin?

A reified type parameter allows you to access the actual type information at runtime inside an inline function, which is normally erased due to type erasure.

intermediate

Why do you need to mark a function as inline to use reified type parameters?

Because only inline functions can keep the type information at runtime by replacing the function call with the actual code, allowing the type to be known and used inside the function.

beginner

How do you declare a function with a reified type parameter?

You declare it with <code>inline</code> and <code>reified</code> keywords like this: <pre>inline fun &lt;reified T&gt; myFunction() { /* use T::class or T::class.java */ }</pre>

intermediate

Give an example use case for reified type parameters.

You can use reified type parameters to check the type at runtime, for example: <pre>inline fun &lt;reified T&gt; isInstance(value: Any) = value is T</pre> This lets you check if a value is of type <code>T</code> without passing the class explicitly.

What keyword must be used with reified type parameters in Kotlin?

A abstract

B open

C inline

D sealed

Reified type parameters require the function to be marked as inline to preserve type information at runtime.

Why can't you normally access generic type information at runtime in Kotlin?

A Because of type erasure

B Because Kotlin doesn't support generics

C Because of inline functions

D Because of null safety

Kotlin uses type erasure on generics, which removes type information at runtime.

Which of these is a valid way to get the class of a reified type parameter T inside an inline function?

A classOf<T>()

B T.class

C T.getClass()

D T::class

Inside an inline function with reified T, you can use T::class to get the Kotlin class reference.

What happens if you try to use reified without inline?

A Compilation error

B Works fine

C Runtime error

D Warning only

Using reified without inline causes a compilation error because the type information cannot be preserved.

Which of these is a benefit of using inline functions with reified type parameters?

A Slower code execution

B Access to type info at runtime

C More memory usage

D No need for generics

Inlining with reified type parameters allows access to the actual type at runtime, which is normally erased.

Explain what reified type parameters are and why they require inline functions in Kotlin.

Think about how Kotlin normally removes generic types and how inline helps keep them.

Describe a simple example where using a reified type parameter makes your Kotlin code easier or cleaner.

Consider how you might check or get the type inside a generic function.