Retrofit 2.6.0: Custom Coroutines CallAdapterFactory

Question

I need to do custom error handling in my api and I wanted to use coroutines with the new version of Retrofit. Since we don't have to use Deferred any longer, our own Jake Wharton wrote this on reddit a month ago

https://github.com/square/retrofit/blob/master/samples/src/main/java/com/example/retrofit/RxJavaObserveOnMainThread.java

But I'm having problems creating the CallAdapterFactory properly.

To be specific, I don't understand: "Delegates to built-in factory and then wraps the value in sealed class"

Is there anyone already using this setup that can help?

Here's the current code

sealed class Results<out T: Any> {
    class Success<out T: Any>(val response: T): Results<T>()
    class Failure(val message: String, val serverError: ServerError?): Results<Nothing>()
    object NetworkError: Results<Nothing>()
}


class ResultsCallAdapterFactory private constructor() : CallAdapter.Factory() {

    companion object {
        @JvmStatic
        fun create() = ResultsCallAdapterFactory()
    }

    override fun get(returnType: Type, annotations: Array<Annotation>, retrofit: Retrofit): CallAdapter<*, *>? {
        return try {
            val enclosedType = returnType as ParameterizedType
            val responseType = getParameterUpperBound(0, enclosedType)
            val rawResultType = getRawType(responseType)
            val delegate: CallAdapter<Any,Any> = retrofit.nextCallAdapter(this,returnType,annotations) as CallAdapter<Any,Any>
            if(rawResultType != Results::class.java)
                null
            else {
                object: CallAdapter<Any,Any>{
                    override fun adapt(call: Call<Any>): Any {
                         val response = delegate.adapt(call)
                        //What should happen here?
                        return response
                    }

                    override fun responseType(): Type {
                        return delegate.responseType()
                    }

                }
            }
        } catch (e: ClassCastException) {
            null
        }

    }
}

`But I'm having problems creating the CallAdapterFactory properly` explain — Zun, Aug 23 '19 at 11:22
"Delegates and then wraps in the sealed class", I don't understand how to do that — Leonardo Deleon, Aug 23 '19 at 11:25
are you using a `SealedClass` because from Jakes context looks like something that has to do with a sealed class. — coroutineDispatcher, Aug 23 '19 at 12:34
@coroutineDispatcher yes, the `Results` sealed class. My question is more about how to use the delegate `CallAdapter` wrap the `Call` to a `Results.Success`, for example — Leonardo Deleon, Aug 23 '19 at 13:20
I'm stuck here https://gist.github.com/leodeleon22/05d313c5e33d120efbc7bfbc79823ccf — Leonardo Deleon, Aug 23 '19 at 20:19
It turned out that it's a duplicate question, please see: [How to create a call adapter for suspending functions in Retrofit?](https://stackoverflow.com/questions/56483235/how-to-create-a-call-adapter-for-suspending-functions-in-retrofit) — Valeriy Katkov, Nov 12 '20 at 18:18

score 1 · Answer 1 · answered Jan 30 '21 at 16:41

1

I've created an example of such a factory, you can find it here on GitHub. Also take a look at a similar question: How to create a call adapter for suspending functions in Retrofit?.

answered Jan 30 '21 at 16:41

Valeriy Katkov

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Retrofit 2.6.0: Custom Coroutines CallAdapterFactory

1 Answers1