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Extension functions
for LiveData
2020.08.21 YUMEMI.apk #1
Hiroyuki Kusu ( @hkusu_ )
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About me
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https://speakerdeck.com/hkusu/unit-test-for-viewmodel-and-livedata
ࠓճ ↑ ʹ࣌ؒతʹؚΊΔ͜ͱ͕ग़དྷͳ͔ͬͨ
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ViewModel தͷ LiveData ͷهड़
private val _liveData1: MutableLiveData = MutableLiveData()
val liveData1: LiveData = _liveData1
val liveData2: LiveData = liveData1.map {
// ...
}
"androidx.lifecycle:lifecycle-livedata-ktx:2.2.0"
• σʔλͷؔ࿈ੑ͕એݴతʹఆٛ͞Ε͍ͯΔͱ͔Γ͍͢
• ͬͱศརʹ͍ͨ͠..!
• ࣗલͰ࡞֦ͨ͠ுؔΛɺ͍͔ͭ͘հ͠·͢
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fun LiveData.coMap(
coroutineScope: CoroutineScope,
coroutineContext: CoroutineContext = coroutineScope.coroutineContext,
block: suspend (T) -> U
): LiveData {
val result = MediatorLiveData()
result.addSource(this) {
coroutineScope.launch(coroutineContext) {
result.postValue(block.invoke(it))
}
}
return result
}
※ switchMap() ͱ livedata {} ΛΈ߹Θͤͯಉ͜͡ͱ͕Ͱ͖·͢
※ ݱঢ়Ͱ inline fun ʹ͢ΔͱམͪΔ https://github.com/Kotlin/kotlinx.coroutines/issues/
coMap
val liveData2: LiveData> = liveData1.coMap(viewModelScope) { it: Int
delay(3_000)
sampleRepository.getItemList(it) // suspending function
} ར༻Πϝʔδ
ؔͷఆٛ
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val liveData3: LiveData = merge(liveData1, liveData2) { i: Int?, b: Boolean? ->
// ...
}
inline fun merge(
liveData1: LiveData,
liveData2: LiveData,
crossinline block: (T1?, T2?) -> U?
): LiveData {
val result = MediatorLiveData()
result.addSource(liveData1) { t1 ->
block.invoke(t1, liveData2.value)?.takeUnless { it is Unit }?.let { result.value = it }
}
result.addSource(liveData2) { t2 ->
block.invoke(liveData1.value, t2)?.takeUnless { it is Unit }?.let { result.value = it }
}
return result
}
merge
ར༻Πϝʔδ
ؔͷఆٛ
(֦ுؔͰͳ͘ී௨ͷؔ)
block தͰ LiveDataͷߋ৽ΛΩϟϯηϧͰ͖ΔΑ͏ʹ͢Δҝͷॲஔ
(Ωϟϯηϧ͍ͨ͠߹null͘͠Γͳ͠Ͱreturn͢Δ)
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val liveData2: LiveData = liveData1.filter {
100 < it
}
inline fun LiveData.filter(
crossinline block: (T) -> Boolean
): LiveData {
val result = MediatorLiveData()
result.addSource(this) {
if (block.invoke(it)) {
result.value = it
}
}
return result
}
filter
ར༻Πϝʔδ
ؔͷఆٛ
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val liveData2: LiveData = liveData1.map {
// ...
}.coMap(viewModelScope) {
// ...
}.map {
// ...
}.coMap(viewModelScope) {
// ...
}.filter {
// ...
}
ͭͳ͛ͯॻ͚Δ
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͋ΔLiveDataͷมߋΛܖػʹͳʹ͔͠ΒͷॲཧΛ͍͕ͨ͠..
( LiveData ͷͭͳ͕Γ͚ͩͰ্ख͘ઃܭͰ͖ͳ͍έʔε )
val liveData2: LiveData = liveData1.map {
}
ແ༻ͳ LiveData2 Λఆٛͯ͠ɺLiveData2 ͷ Observer ͕ډͳ͍߹
͜ͷϒϩοΫ࣮ߦ͞Εͳ͍
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val observe = liveData1.map {
}.observe()
// ...
override fun onCleared() {
observe.cancel()
}
class Observe(private val liveData: LiveData) {
private val observer = Observer {}
fun start() {
liveData.observeForever(observer)
}
fun cancel() {
liveData.removeObserver(observer)
}
}
fun LiveData.observe(): Observe = Observe(this).apply { start() }
observe
ViewModel ͷഁغ࣌ʹ؍ଌΛऴྃͤ͞Δඞཁ
observeForever Λར༻
͜ͷϒϩοΫͰҙͷॲཧ
ؔͷఆٛ
ར༻Πϝʔδ
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https://gist.github.com/hkusu/b258c4e4ef488ccd8b213586417ffbec
ࠓճɺհ֦ͨ͠ுؔgistʹஔ͖·ͨ͠
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Thank you !
@hkusu_