Kotlin extension for LiveData, chaining like RxJava.
To add LiveData KTX to your project, add the following to your app module's build.gradle:
implementation "com.shopify:livedata-ktx:VERSION"val liveData = MutableLiveData<Boolean>()
liveData
.distinct()
.filter { it == false }
.map { true }
.nonNull()
.observe(lifecycleOwner, { result ->
// result is non-null and always true
})val liveData = MutableLiveData<Boolean>()
liveData
.distinct()
.observe(lifecycleOwner, {
// TODO
})val liveData = MutableLiveData<Boolean>()
liveData
.distinct()
.observe({
// TODO
})val mutableLiveData = MutableLiveData<Boolean>()
val liveData: LiveData<Boolean> = mutableLiveData.distinct()
// liveData.value is invalid
val singleLiveData = SingleLiveData<Boolean>()
val nonNullLiveData: NonNullLiveData<Boolean> = singleLiveData
// nonNullLiveData.value is invalid
val nonNullMutableLiveData = MutableLiveData<Boolean>()
val otherNonNullLiveData: NonNullLiveData<Boolean> = nonNullMutableLiveData.nonNull()
// otherNonNullLiveData is invalidBecause the input observer goes through a wrapper before it observes to source LiveData. So that you can't simply remove it by just calling origin method liveData.removeObserver.
The new observe method returns Removable interface that allows you to remove observer effectively.
val liveData = MutableLiveData<Boolean>()
val removable = liveData
.nonNull()
.observe(lifecycleOwner, {
// TODO
})
removable.removeObserver()
val removableFromObserveForever = liveData.observe {
// TODO
}
removableFromObserveForever.removeObserver()It is a lifecycle-aware observable that sends only new updates after subscription, used for events like navigation and Snackbar messages. livedata-ktx has different implementation comparing to SingleLiveEvent from google samples android-architecture.
val liveData = SingleLiveData<Int>()
val actuals: MutableList<Int?> = mutableListOf()
val observer: (t: Int) -> Unit = { actuals.add(it) }
liveData.value = 1
liveData.observe(this, observer)
liveData.value = 2
liveData.value = 3
val expecteds = mutableListOf(2, 3)
assertEquals(expecteds, actuals)For more use cases, please see the tests at LiveDataTest.kt
It is easy to add your custom extension without requiring to send a PR. For example:
/**
* filter
*/
internal class FilterExt<T>(private val predicate: (T?) -> Boolean) : Operator<T, T> {
override fun run(value: T?, source: LiveData<T>, onResult: OnResult<T>) {
val predicated = predicate(value)
onResult(Result(value, !predicated))
}
}
fun <T> LiveData<T>.filter(predicate: (T?) -> Boolean): LiveData<T> = SupportLiveData(this, FilterExt<T>(predicate))
fun <T> NonNullLiveData<T>.filter(predicate: (T) -> Boolean): NonNullLiveData<T> = SupportNonNullLiveData(this, FilterExt {
predicate(it!!)
})Any contributions are welcome! Please check the CONTRIBUTING guideline before submitting a new issue. Wanna send PR? Click HERE
- Francisco Cavedon <@fcavedon>
- Henry Tao <@henrytao-me>
- Ivan Savytskyi <@sav007>
- Kris Orr <@krisorr>
The MIT License (MIT)
Copyright (c) 2018 Shopify Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.