Kotlin Koans—Part 1

I read that Android is going to officially support Kotlin now. Last year, I bought the IntelliJ IDE and one of the first things I noticed was that the IDE offered to make Kotlin classes. I had never done anything with Kotlin but I often wondered about it. It looked interesting to me, but now that Google has thrown in with Kotlin, I decided to give it try for myself.

This is the first in a series of posts where I’m going to work through the tutorials provided on kotlinlang.org. This first post was on the very first tutorial, which is the classical ‘Hello World’ style problem.

I started by cloning the github project that they give you. Here is what I got presented with.

package i_introduction._0_Hello_World

import util.TODO
import util.doc0

fun todoTask0(): Nothing = TODO(
    """
        Introduction.

        Kotlin Koans project consists of 42 small tasks for you to solve.
        Typically you'll have to replace the function invocation 'todoTaskN()', which throws an exception,
        with the correct code according to the problem.

        Using 'documentation =' below the task description you can open the related part of the online documentation.
            Press 'Ctrl+Q'(Windows) or 'F1'(Mac OS) on 'doc0()' to call the "Quick Documentation" action;
            "See also" section gives you a link.
            You can see the shortcut for the "Quick Documentation" action used in your IntelliJ IDEA
            by choosing "Help -> Find Action..." (in the top menu), and typing the action name ("Quick Documentation").
            The shortcut in use will be written next to the action name.

        Using 'references =' you can navigate to the code mentioned in the task description.

        Let's start! Make the function 'task0' return "OK".
    """,
    documentation = doc0(),
    references = { task0(); "OK" }
)

fun task0(): String {
    return todoTask0()
}

My job was to make the function task0 was to make it return “OK”. It wasn’t too painful. I just had to update task0

fun task0(): String {
    return "OK"
}

Once I did this, I ran the unit test that they give you to check if you did the task properly. This was easy to do in IntelliJ. The IDE provides you with a button to click on to run the test.

After I ran the test, I got the output the test was expecting.