Kotlin Programming: The Big Nerd Ranch Guide, First Edition

Specifying a Coroutine with async

One way to create a coroutine is to use the async function provided with the coroutine library. The async function requires one argument: a lambda that specifies the work you want to happen in the background.

In fetchCharacterData, move the blocking readText function call into a lambda and pass it to the async function. Also, update the return type to be a Deferred<CharacterGenerator.CharacterData>, the result of the async function:

Listing 22.7  Making fetchCharacterData async (CharacterGenerator.kt)

    ...
    fun fetchCharacterData(): Deferred<CharacterGenerator.CharacterData> {
        return async {
            val apiData = URL(CHARACTER_DATA_API).readText()
            return CharacterGenerator.fromAPIData(apiData)
        } }  ...