Is there a better way to write this? ```state.myList[index] = state.myList[index].copy(isFollowing ...

# getting-started

[Colton Idle]

Is there a better way to write this?

state.myList[index] = state.myList[index].copy(isFollowing = !state.myList[index].isFollowing!!)

A lot of ceremony just to flip the value of isFollowing

[Sam]

Might be overkill, but if you have a lot of use cases like this you could look at #arrow optics

[Sam]

There’s also https://youtrack.jetbrains.com/issue/KT-44653 for the proposed “copy var” syntax but it’s gone a bit quiet, and I also don’t know if it would support your use case of indexing into a list

[Sam]

As far as the current language capabilities, the best I can think of is to use a helper function something like this:

fun <T> MutableList<T>.update(i: Int, f: (T) -> T) {
    this[i] = f(this[i])
}

Then you can write

state.myList.update(index) {
    it.copy(isFollowing = !it.isFollowing!!)
}

[Colton Idle]

Oh. I like the helper function. Seems like I could use it all over the place. thanks!

[Rob Elliot]

Could also add a helper function to the type of state.myList[index] to flip the status of `isFollowing`:

fun MyType.toggleFollowing() = copy(isFollowing = !isFollowing)

Then it's:

state.myList.update(1) { it.toggleFollowing() }

[August Lilleaas]

I have my fingers crossed for “update” on lists and maps as a part of the standard library 😄 I use those functions in Clojure all the time