How to cancel a coroutine inside the coroutine? Something like in normal coding, I can do `return`, ...

# coroutines

[albertgao]

How to cancel a coroutine inside the coroutine? Something like in normal coding, I can do return, then the statement after this return will not be executed. But what about inside a coroutine? You can’t return in a coroutine. Seems the answer is coroutineContext().cancel(), But with Anko, it said coroutineContext of type CoroutineContext can't be invoked as a function

[gildor]

Could you show some sample code

[gildor]

coroutineContext of type CoroutineContext can’t be invoked as a function

Because coroutineContext is not a function, but property, please check docs of kotlinx.coroutines

[albertgao]

For this, i suppose i just need to introduce real kotlin coroutine rather than the Anko one.

[albertgao]

The code is here:

private fun handleLogDetails() = launch(UI){

        val result:HttpResponse = bg {
            authHelper.logDetails()
        }.await()

        if (result.error) {
            showErrorDialog(result.errorMessage)
            throw CancellationException()
        }
        
        // do something when no error in result
        // how to return above if I don't want to write if else
        
    }

[gildor]

For this, i suppose i just need to introduce real kotlin coroutine rather than the Anko one.

Anko uses “real coroutines”, just update version of kotlinx.coroutines in your project

[gildor]

Just use return instead of Cancellation:

if (result.error) {
             showErrorDialog(result.errorMessage)
        return@launch
    }

[albertgao]

Save my day! Thanks

[albertgao]

I use coroutine by adding these:

implementation "org.jetbrains.anko:anko-coroutines:$anko_version"
    implementation "org.jetbrains.anko:anko-sdk25-coroutines:$anko_version"
    implementation "org.jetbrains.anko:anko-appcompat-v7-coroutines:$anko_version"

No kotlin coroutine here, is it fine?

[gildor]

It’s fine, but you use transitive version of kotlinx.coroutines, I would just remove org.jetbrains.anko:anko-coroutines and add

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:0.22.5'
compile 'org.jetbrains.kotlinx:kotlinx-coroutines-android:0.22.5'

[gildor]

If you use bg or asReference just copy them to your project

[gildor]

asReference actually would be helpful for your case, because looks like your blocking network request is non-cancellable to avoid memory leasks

[albertgao]

Really thanks!

1. For that gradle, could I remove that anko-sdk25-coroutines and anko-appcompat-v7-coroutines? With just use the two you mentoined?

2. Every time I need to invoke some methods from activity class inside a coroutine, if my API doesn’t support cancellation which is exactly my case. I should use the asReference() as a bridge to invoke activity methods to avoid mem leak, right?

[gildor]

Yes, you can try, depends which APIs of anko you use.
You can keep using them, just update Kotlin.dependency (add them explicitly)