Function onChanged

app/src/main/java/androidx/lifecycle/Transformations.kt:166–178

            var liveData: LiveData<Y>? = null

            override fun onChanged(value: X) {
                val newLiveData = switchMapFunction.apply(value)
                if (liveData === newLiveData) {
                    return
                }
                if (liveData != null) {
                    result.removeSource(liveData!!)
                }
                liveData = newLiveData
                if (liveData != null) {
                    result.addSource(liveData!!) { y -> result.setValue(y) }
                }
            }
        },
    )
    return result