If I have code that previously used the continuati...

# coroutines

[Allan Wang]

If I have code that previously used the continuation style:

doA {
  doB {
    doC()
  }
}

And I want to make them all in the same level, would it be done like the following?

// Original
fun doA(continuation: () -> Unit) {
  // some action
  continuation()
}

// New
suspend fun doA() = suspendCoroutine<Unit> {
  // some action
  it.resume(Unit)
}

Then I do something like

launch {
  doA()
  doB()
  doC()
}

Which should occur one after the other by default.

My goal is just to remove the nested brackets. The reason I have continuation to begin with is that the actions I’m running deal with callbacks.

Is there also a benefit to doing some potential safety checks before calling suspendCoroutine vs putting them all inside that wrapper? The delay function seems to do that.

[gildor]

But I don't see any usage of callback here, why not just write your code sequentially, it's not clear for those examples why do you need callback and suspend

[Allan Wang]

This is an example of an actual method I have:

private fun setWebCookie(cookie: String?, callback: (() -> Unit)?) {
    with(CookieManager.getInstance()) {
        removeAllCookies { _ ->
            if (cookie == null) {
                callback?.invoke()
                return@removeAllCookies
            }
            L.d { "Setting cookie" }
            val cookies = cookie.split(";").map { Pair(it, SingleSubject.create<Boolean>()) }
            cookies.forEach { (cookie, callback) -> setCookie(FB_URL_BASE, cookie) { callback.onSuccess(it) } }
            Observable.zip<Boolean, Unit>(cookies.map { (_, callback) -> callback.toObservable() }) {}
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe {
                        callback?.invoke()
                        L.d { "Cookies set" }
                        L._d { cookie }
                        flush()
                    }
        }
    }
}

In android, remove all cookies and set cookies all take callbacks. I want to clear all cookies and then get set a bunch of cookies, before performing actions. All the other methods are similar.

[Allan Wang]

Github link for syntax highlighting: https://github.com/AllanWang/Frost-for-Facebook/blob/master/app/src/main/kotlin/com/pitchedapps/frost/facebook/FbCookie.kt#L31

[Dico]

I think you should replace the implementation of your doA, doB and doC with suspend function and remove the callback parameters

[Dico]

Then you can call them sequentially from coroutine

[gildor]

+1 to Dico, you just need suspend version of `removeAllCookies`/`setCookie`

[gildor]

You need something like that:

suspend fun CookieManager.removeAllCookiesSuspend(): Boolean {
        return suspendCoroutine { cont ->
            removeAllCookies {
                cont.resume(it)
            }
        }
    }

[gildor]

I actually not sure why do you need Rx in this case

[gildor]

I think this function in general not really good, why do you want call callback on every cookie set you can just return result

[gildor]

and with coroutines you don’t need this Rx just to switch to main thread, you can use coroutines dispatcher for thaat