Funny, I read this this morning in the subway K Helped me understand and write this dirty line:

inline fun <reified T> getList(json: String): T? = Gson().fromJson<T>(json, object : TypeToken<T>() {}.type)

(used to deserialize an ArrayList of custom objects)

is

getList

the name you want for that method?

val user = getList<User>(json)

doesn't seem right to me

Actually I use it directly as a parameter so it looks like:

fun newList() { /* create & populate a new list */ }
fun someFunction(list: ArrayList<SomeObject>) { ... }

someFunction(getList(json) ?: newList())

I don't clearly understand exactly why but I don't need to specify

<ArrayList<SomeObject>>

before the parenthesis somehow

You don't need to specify the type, because the compiler can infer it.

Infer it meaning it determines it by "reading" the type of the function parameter?

You could put it like that, yes.

Well, thanks for your input and explanations, it appreciated 🙂

Thanks for this. I didn't know you could do this with reified generics

@kevinmost Fixed the line to

inline fun <reified T> Gson.getList(json: String): T? = fromJson<T>(json, object : TypeToken<T>() {}.type)

You could also think about caching the type token

Is this possible in a file where I grouped extensions? (no classes)

You can use reified type parameters on any inline function, extension or not.

@diesieben07 I was asking about caching

TypeToken

, my guess is that I should

val

it but does it work outside a

class

?

You can't really cache the

TypeToken

, since you don't have anything to cache by (i.e. you don't have a key for the cache).

Ok I see now, thanks for the explanation 🙂