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Ryutaro Miyashita
Ryutaro Miyashita

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How to make reusable CompositeDisposable and Kotlin extension

#android #rxjava #kotlin

Prepare

app/build.gradle 

ext { rxjava2_version = "2.1.7" } dependencies { implementation "io.reactivex.rxjava2:rxjava:${rxjava2_version}" }
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Make "AndroidDisposable"

Edit

The same effect can be obtained by using "CompositeDisposable#clear"

CompositeDisposable is can not reuse when already disposed. If you want sync disposable lifecycle with Android Activity lifecycle, it is possible to correspond by making simple wrapper.

class AndroidDisposable { private var compositeDisposable: CompositeDisposable? = null fun add(disposable: Disposable) { if (compositeDisposable == null) { compositeDisposable = CompositeDisposable() } compositeDisposable?.add(disposable) } fun dispose() { compositeDisposable?.dispose() compositeDisposable = null } }
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How to use 

class MainActivity : AppCompatActivity() { private disposable = AndroidDisposable() override fun onStart() { super.onStart() disposable.add(/* Some disposable */) } override fun onStop() { disposable.dispose() super.onStop() } }
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Kotlin Extension

Kotlin can add new function / method for existing class (An entity is a static method that takes an instance of the target class as the first argument). I will extend Disposable and make it easy to use AndroidDisposable.

operator fun AndroidDisposable.plusAssign(disposable: Disposable) { add(disposable) } fun Disposable.addTo(androidDisposable: AndroidDisposable): Disposable = apply { androidDisposable.add(this) }
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How to use 

val texts = listOf("1", "2", "3") // Operator disposable += Observable.fromIterable(texts) .map { it.toInt(10) } .reduce { t1, t2 -> t1 + t2 } .subscribe() // or Observable.fromIterable(texts) .map { it.toInt(10) } .reduce { t1, t2 -> t1 + t2 } .subscribe() .addTo(disposable)
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Top comments (1)

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Gideon Steven Tobing •

hi, im just curious abit about, why should you put composite disposable onStart() ?