refactor: use ViewState to handle ViewModel properties. (#19)

use a ViewState sealed class to model all possibles states of a ViewModel
fix LiveData nullability on BindingAdapters

closes #9

Author: ffgiraldez

app/src/main/java/es/ffgiraldez/comicsearch/search/presentation/SearchViewModel.kt

@@ -2,7 +2,6 @@ package es.ffgiraldez.comicsearch.search.presentation
 
 import android.arch.lifecycle.MutableLiveData
 import android.arch.lifecycle.ViewModel
-import android.util.Log
 import es.ffgiraldez.comicsearch.comics.ComicRepository
 import es.ffgiraldez.comicsearch.comics.Volume
 import es.ffgiraldez.comicsearch.platform.toFlowable
@@ -11,21 +10,29 @@ class SearchViewModel(
         private val repo: ComicRepository
 ) : ViewModel() {
 
-    val loading: MutableLiveData<Boolean> = MutableLiveData()
     val query: MutableLiveData<String> = MutableLiveData()
+    val loading: MutableLiveData<Boolean> = MutableLiveData()
     val results: MutableLiveData<List<Volume>> = MutableLiveData()
 
     init {
-        loading.value = false
-        results.value = emptyList()
         query.toFlowable()
-                .doOnNext { loading.postValue(true) }
-                .doOnNext { results.postValue(emptyList()) }
-                .switchMap { repo.findVolume(it) }
-                .doOnNext { loading.postValue(false) }
+                .switchMap {
+                    repo.findVolume(it)
+                            .map { SearchViewState.result(it) }
+                            .startWith(SearchViewState.loading())
+                }.startWith(SearchViewState.idle())
                 .subscribe {
-                    results.postValue(it)
-                    Log.d("cambio", "busqueda completa [${it.size}] volumenes encontrados")
+                    when (it) {
+                        SearchViewState.Idle -> applyState(false, emptyList())
+                        is SearchViewState.Loading -> applyState(true, emptyList())
+                        is SearchViewState.Result -> applyState(false, it.volumeList)
+                    }
                 }
+
+    }
+
+    private fun applyState(isLoading: Boolean, volumeList: List<Volume>) {
+        loading.postValue(isLoading)
+        results.postValue(volumeList)
     }
 }

app/src/main/java/es/ffgiraldez/comicsearch/search/presentation/SearchViewState.kt

@@ -0,0 +1,17 @@
+package es.ffgiraldez.comicsearch.search.presentation
+
+import es.ffgiraldez.comicsearch.comics.Volume
+
+sealed class SearchViewState {
+
+    companion object {
+        fun result(volumeList: List<Volume>): SearchViewState = Result(volumeList)
+        fun idle(): SearchViewState = Idle
+        fun loading(): SearchViewState = Loading
+    }
+
+    object Idle : SearchViewState()
+    object Loading : SearchViewState()
+    data class Result(val volumeList: List<Volume>) : SearchViewState()
+
+}

app/src/main/java/es/ffgiraldez/comicsearch/search/ui/SearchBindingAdapters.kt

@@ -27,13 +27,13 @@ fun bindSuggestionClick(search: FloatingSearchView, clickConsumer: ClickConsumer
  * Limit scope to apply using RecyclerView as BindingAdapter
  */
 @BindingAdapter("adapter", "on_data_change", "on_selected", requireAll = false)
-fun bindData(recycler: RecyclerView, searchAdapter: SearchVolumeAdapter, data: List<Volume>, consumer: OnVolumeSelectedListener) =
+fun bindData(recycler: RecyclerView, searchAdapter: SearchVolumeAdapter, data: List<Volume>?, consumer: OnVolumeSelectedListener) =
         with(recycler) {
             if (adapter == null) {
                 adapter = searchAdapter
                 searchAdapter.onVolumeSelectedListener = consumer
             }
-            searchAdapter.submitList(data)
+            data?.let { searchAdapter.submitList(data) }
         }
 
 

app/src/main/java/es/ffgiraldez/comicsearch/search/ui/SearchScreenDelegate.kt

@@ -20,4 +20,3 @@ class SearchScreenDelegate(
 
     fun onSuggestionSelected(suggestion: String) =
             with(search) { query.value = suggestion }
-}

app/src/main/java/es/ffgiraldez/comicsearch/sugestion/presentation/SuggestionViewModel.kt

@@ -2,7 +2,6 @@ package es.ffgiraldez.comicsearch.sugestion.presentation
 
 import android.arch.lifecycle.MutableLiveData
 import android.arch.lifecycle.ViewModel
-import android.util.Log
 import es.ffgiraldez.comicsearch.comics.ComicRepository
 import es.ffgiraldez.comicsearch.platform.toFlowable
 import java.util.concurrent.TimeUnit
@@ -16,17 +15,25 @@ class SuggestionViewModel(
     val results: MutableLiveData<List<String>> = MutableLiveData()
 
     init {
-        loading.value = false
-        results.value = emptyList()
         query.toFlowable()
                 .debounce(400, TimeUnit.MILLISECONDS)
-                .doOnNext { loading.postValue(true) }
-                .doOnNext { results.postValue(emptyList()) }
-                .switchMap { repo.findSuggestion(it) }
-                .doOnNext { loading.postValue(false) }
+                .switchMap { query ->
+                    repo.findSuggestion(query)
+                            .map { suggestions -> SuggestionViewState.result(suggestions) }
+                            .startWith(SuggestionViewState.loading())
+                }.startWith(SuggestionViewState.idle())
                 .subscribe {
-                    Log.d("cambio", "$it")
-                    results.postValue(it)
+                    when (it) {
+                        SuggestionViewState.Idle -> applyState(false, emptyList())
+                        is SuggestionViewState.Loading -> applyState(true, emptyList())
+                        is SuggestionViewState.Result -> applyState(false, it.suggestions)
+                    }
                 }
+
+    }
+
+    private fun applyState(isLoading: Boolean, suggestions: List<String>) {
+        loading.postValue(isLoading)
+        results.postValue(suggestions)
     }
 }

app/src/main/java/es/ffgiraldez/comicsearch/sugestion/presentation/SuggestionViewState.kt

@@ -0,0 +1,15 @@
+package es.ffgiraldez.comicsearch.sugestion.presentation
+
+sealed class SuggestionViewState {
+
+    companion object {
+        fun result(suggestions: List<String>): SuggestionViewState = Result(suggestions)
+        fun idle(): SuggestionViewState = Idle
+        fun loading(): SuggestionViewState = Loading
+    }
+
+    object Idle : SuggestionViewState()
+    object Loading : SuggestionViewState()
+    data class Result(val suggestions: List<String>) : SuggestionViewState()
+
+}

app/src/main/java/es/ffgiraldez/comicsearch/sugestion/ui/SuggestionBindingAdapters.kt

@@ -9,11 +9,14 @@ fun bindQueryChangeListener(search: FloatingSearchView, listener: FloatingSearch
         search.setOnQueryChangeListener(listener)
 
 @BindingAdapter("suggestions")
-fun bindSuggestions(search: FloatingSearchView, liveData: List<String>) =
-        liveData.map { VolumeSearchSuggestion(it) }.let { search.swapSuggestions(it) }
+fun bindSuggestions(search: FloatingSearchView, liveData: List<String>?) = liveData?.let {
+    it.map { VolumeSearchSuggestion(it) }.let { search.swapSuggestions(it) }
+}
 
 @BindingAdapter("show_progress")
-fun bindLoading(search: FloatingSearchView, liveData: Boolean) = when (liveData) {
-    true -> search.showProgress()
-    false -> search.hideProgress()
+fun bindLoading(search: FloatingSearchView, liveData: Boolean?) = liveData?.let {
+    when (it) {
+        true -> search.showProgress()
+        false -> search.hideProgress()
+    }
 }