Revision control
Copy as Markdown
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
package org.mozilla.tv.firefox.ext
import androidx.lifecycle.LiveData
import androidx.lifecycle.MediatorLiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Transformations
fun <T, U> LiveData<T>.map(mapper: (T) -> U): LiveData<U> {
return Transformations.map(this, mapper)
}
fun <T> LiveData<T>.doOnEach(action: (T?) -> Unit): LiveData<T> {
return this.map {
action(it)
it
}
}
fun <T> MutableLiveData<T>.postIfNew(new: T) {
val old = this.value
if (new != old) this.postValue(new)
}
object LiveDataCombiners {
// If more advanced versions of this are required, we should import RxJava instead of duplicating their effort #1783
// Note: CursorViewModel.isEnabled combines 3 streams by calling this twice
fun <T, U, R> combineLatest(
source1: LiveData<T>,
source2: LiveData<U>,
combiner: (T, U) -> R
): LiveData<R> {
val result = MediatorLiveData<R>()
val merge = merge@{
val source1Value = source1.value ?: return@merge
val source2Value = source2.value ?: return@merge
result.value = combiner(source1Value, source2Value)
}
result.addSource(source1) { merge.invoke() }
result.addSource(source2) { merge.invoke() }
return result
}
}