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I have some problem. I'm a beginer in RxJava/RxKotlin/RxAndroid, and dont understand some features. For Example:
import rus.pifpaf.client.data.catalog.models.Category
import rus.pifpaf.client.data.main.MainRepository
import rus.pifpaf.client.data.main.models.FrontDataModel
import rus.pifpaf.client.data.product.models.Product
import rx.Observable
import rx.Single
import rx.lang.kotlin.observable
import java.util.*
class MainInteractor {
private var repository: MainRepository = MainRepository()
fun getFrontData() {
val cats = getCategories()
val day = getDayProduct()
val top = getTopProducts()
return Observable.zip(cats, day, top, MainInteractor::convert)
}
private fun getTopProducts(): Observable<List<Product>> {
return repository.getTop()
.toObservable()
.onErrorReturn{throwable -> ArrayList() }
}
private fun getDayProduct(): Observable<Product> {
return repository.getSingleProduct()
.toObservable()
.onErrorReturn{throwable -> Product()}
}
private fun getCategories(): Observable<List<Category>> {
return repository.getCategories()
.toObservable()
.onErrorReturn{throwable -> ArrayList() }
}
private fun convert(cats: List<Category>, product: Product, top: List<Product>): FrontDataModel {
}
}
Then I'm use MainInteractor::convert Android studio tell me next
I tried a lot of variant and tried to understand what does it want, but no success. Help me please... Best Regards.
323
Zip operator is used to combine emission from multiple observable into a single observable. Zip Operator Works in Sequence. That means each observable will be executed sequentially. So as we see the output source2 only emits item after source1 has emitted all items.
The Zip method returns an Observable that applies a function of your choosing to the combination of items emitted, in sequence, by two (or more) other Observables, with the results of this function becoming the items emitted by the returned Observable.
Kotlin Extensions for RxJava RxKotlin is a lightweight library that adds convenient extension functions to RxJava. You can use RxJava with Kotlin out-of-the-box, but Kotlin has language features (such as extension functions) that can streamline usage of RxJava even more.
There are two key types to understand when working with Rx: Observable represents any object that can get data from a data source and whose state may be of interest in a way that other objects may register an interest. An observer is any object that wishes to be notified when the state of another object changes.
You can also explicitly specify the Function3 type in the lambda Like :
Observable.zip(cats,
day,
top,
Function3<List<Product>, Product, List<Category>, FrontDataModel>
{ cats, day, top -> convert(cats, day, top) }
and play with the IntelliJ idea shortcut alt+enter to display more actions and change the displaying format of the high-order function.
Why Function3?
Following The Functional Interfaces if it has two Input params it's a BiFunction and if it has 3 Inputs it's a Function3 and the list goes on.
54
Just replace function reference with lambda:
return Observable.zip(cats, day, top, { c, d, t -> convert(c, d, t) })
And don't forget to declare function's return type explicitly:
fun getFrontData(): Observable<FrontDataModel> {
...
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