Refactor | Added extension functions

app/src/main/java/com/google/samples/apps/nowinandroid/MainActivityViewModel.kt

@@ -22,24 +22,19 @@ import com.google.samples.apps.nowinandroid.MainActivityUiState.Loading
 import com.google.samples.apps.nowinandroid.MainActivityUiState.Success
 import com.google.samples.apps.nowinandroid.core.data.repository.UserDataRepository
 import com.google.samples.apps.nowinandroid.core.model.data.UserData
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.map
-import kotlinx.coroutines.flow.stateIn
 
 @HiltViewModel
 class MainActivityViewModel @Inject constructor(
     userDataRepository: UserDataRepository
 ) : ViewModel() {
     val uiState: StateFlow<MainActivityUiState> = userDataRepository.userDataStream.map {
         Success(it)
-    }.stateIn(
-        scope = viewModelScope,
-        initialValue = Loading,
-        started = SharingStarted.WhileSubscribed(5_000)
-    )
+    }.stateInScope(viewModelScope, initialValue = Loading)
 }
 
 sealed interface MainActivityUiState {

app/src/main/java/com/google/samples/apps/nowinandroid/ui/NiaAppState.kt

@@ -36,6 +36,7 @@ import androidx.navigation.navOptions
 import androidx.tracing.trace
 import com.google.samples.apps.nowinandroid.core.data.util.NetworkMonitor
 import com.google.samples.apps.nowinandroid.core.ui.TrackDisposableJank
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import com.google.samples.apps.nowinandroid.feature.bookmarks.navigation.bookmarksRoute
 import com.google.samples.apps.nowinandroid.feature.bookmarks.navigation.navigateToBookmarks
 import com.google.samples.apps.nowinandroid.feature.foryou.navigation.forYouNavigationRoute
@@ -47,9 +48,7 @@ import com.google.samples.apps.nowinandroid.navigation.TopLevelDestination.BOOKM
 import com.google.samples.apps.nowinandroid.navigation.TopLevelDestination.FOR_YOU
 import com.google.samples.apps.nowinandroid.navigation.TopLevelDestination.INTERESTS
 import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.map
-import kotlinx.coroutines.flow.stateIn
 
 @Composable
 fun rememberNiaAppState(
@@ -95,11 +94,7 @@ class NiaAppState(
 
     val isOffline = networkMonitor.isOnline
         .map(Boolean::not)
-        .stateIn(
-            scope = coroutineScope,
-            started = SharingStarted.WhileSubscribed(5_000),
-            initialValue = false
-        )
+        .stateInScope(coroutineScope, initialValue = false)
 
     /**
      * Map of top level destinations to be used in the TopBar, BottomBar and NavRail. The key is the

core/ui/src/main/java/com/google/samples/apps/nowinandroid/core/ui/Extenstions.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.core.ui
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.stateIn
+
+/**
+ * This is a helper extension function for making it easier to use [Flow.stateIn] within a ViewModel or etc.
+ * @Returns a [StateFlow] that shares the latest value emitted by the original [Flow] and starts
+ * with the [initialValue].
+ */
+fun <T> Flow<T>.stateInScope(
+    coroutineScope: CoroutineScope,
+    started: SharingStarted = SharingStarted.WhileSubscribed(5_000),
+    initialValue: T
+): StateFlow<T> = stateIn(coroutineScope, started, initialValue)

feature/author/src/main/java/com/google/samples/apps/nowinandroid/feature/author/AuthorViewModel.kt

@@ -27,16 +27,18 @@ import com.google.samples.apps.nowinandroid.core.domain.model.FollowableAuthor
 import com.google.samples.apps.nowinandroid.core.domain.model.SaveableNewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.Author
 import com.google.samples.apps.nowinandroid.core.result.Result
+import com.google.samples.apps.nowinandroid.core.result.Result.Error
+import com.google.samples.apps.nowinandroid.core.result.Result.Loading
+import com.google.samples.apps.nowinandroid.core.result.Result.Success
 import com.google.samples.apps.nowinandroid.core.result.asResult
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import com.google.samples.apps.nowinandroid.feature.author.navigation.AuthorArgs
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.map
-import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 
 @HiltViewModel
@@ -54,20 +56,11 @@ class AuthorViewModel @Inject constructor(
         authorId = authorArgs.authorId,
         userDataRepository = userDataRepository,
         authorsRepository = authorsRepository
-    )
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5_000),
-            initialValue = AuthorUiState.Loading
-        )
+    ).stateInScope(viewModelScope, initialValue = AuthorUiState.Loading)
 
-    val newsUiState: StateFlow<NewsUiState> =
-        getSaveableNewsResourcesStream.newsUiStateStream(authorId = authorArgs.authorId)
-            .stateIn(
-                scope = viewModelScope,
-                started = SharingStarted.WhileSubscribed(5_000),
-                initialValue = NewsUiState.Loading
-            )
+    val newsUiState: StateFlow<NewsUiState> = getSaveableNewsResourcesStream
+        .newsUiStateStream(authorId = authorArgs.authorId)
+        .stateInScope(viewModelScope, initialValue = NewsUiState.Loading)
 
     fun followAuthorToggle(followed: Boolean) {
         viewModelScope.launch {
@@ -80,49 +73,54 @@ class AuthorViewModel @Inject constructor(
             userDataRepository.updateNewsResourceBookmark(newsResourceId, bookmarked)
         }
     }
-}
 
-private fun authorUiStateStream(
-    authorId: String,
-    userDataRepository: UserDataRepository,
-    authorsRepository: AuthorsRepository,
-): Flow<AuthorUiState> {
-    // Observe the followed authors, as they could change over time.
-    val followedAuthorIdsStream: Flow<Set<String>> =
-        userDataRepository.userDataStream
-            .map { it.followedAuthors }
-
-    // Observe author information
-    val authorStream: Flow<Author> = authorsRepository.getAuthorStream(
-        id = authorId
-    )
-
-    return combine(
-        followedAuthorIdsStream,
-        authorStream,
-        ::Pair
-    )
-        .asResult()
-        .map { followedAuthorToAuthorResult ->
-            when (followedAuthorToAuthorResult) {
-                is Result.Success -> {
-                    val (followedAuthors, author) = followedAuthorToAuthorResult.data
-                    val followed = followedAuthors.contains(authorId)
-                    AuthorUiState.Success(
-                        followableAuthor = FollowableAuthor(
-                            author = author,
-                            isFollowed = followed
-                        )
-                    )
-                }
-                is Result.Loading -> {
-                    AuthorUiState.Loading
-                }
-                is Result.Error -> {
-                    AuthorUiState.Error
-                }
+    private fun authorUiStateStream(
+        authorId: String,
+        userDataRepository: UserDataRepository,
+        authorsRepository: AuthorsRepository,
+    ): Flow<AuthorUiState> {
+        // Observe the followed authors, as they could change over time.
+        val followedAuthorIdsStream: Flow<Set<String>> =
+            userDataRepository.userDataStream.map { it.followedAuthors }
+
+        // Observe author information
+        val authorStream: Flow<Author> = authorsRepository.getAuthorStream(
+            id = authorId
+        )
+
+        return combine(
+            followedAuthorIdsStream,
+            authorStream,
+            ::Pair
+        )
+            .asResult()
+            .map { followedAuthorToAuthorResult ->
+                handleToAuthorResult(followedAuthorToAuthorResult, authorId)
             }
-        }
+    }
+
+    private fun handleToAuthorResult(
+        followedAuthorToAuthorResult: Result<Pair<Set<String>, Author>>,
+        authorId: String
+    ) = when (followedAuthorToAuthorResult) {
+        is Success -> onSuccessResult(followedAuthorToAuthorResult, authorId)
+        is Loading -> AuthorUiState.Loading
+        is Error -> AuthorUiState.Error
+    }
+
+    private fun onSuccessResult(
+        followedAuthorToAuthorResult: Success<Pair<Set<String>, Author>>,
+        authorId: String
+    ): AuthorUiState.Success {
+        val (followedAuthors, author) = followedAuthorToAuthorResult.data
+        val followed = followedAuthors.contains(authorId)
+        return AuthorUiState.Success(
+            followableAuthor = FollowableAuthor(
+                author = author,
+                isFollowed = followed
+            )
+        )
+    }
 }
 
 private fun GetSaveableNewsResourcesStreamUseCase.newsUiStateStream(
@@ -134,9 +132,9 @@ private fun GetSaveableNewsResourcesStreamUseCase.newsUiStateStream(
     ).asResult()
         .map { newsResult ->
             when (newsResult) {
-                is Result.Success -> NewsUiState.Success(newsResult.data)
-                is Result.Loading -> NewsUiState.Loading
-                is Result.Error -> NewsUiState.Error
+                is Success -> NewsUiState.Success(newsResult.data)
+                is Loading -> NewsUiState.Loading
+                is Error -> NewsUiState.Error
             }
         }
 }

feature/bookmarks/src/main/java/com/google/samples/apps/nowinandroid/feature/bookmarks/BookmarksViewModel.kt

@@ -23,14 +23,13 @@ import com.google.samples.apps.nowinandroid.core.domain.GetSaveableNewsResources
 import com.google.samples.apps.nowinandroid.core.domain.model.SaveableNewsResource
 import com.google.samples.apps.nowinandroid.core.ui.NewsFeedUiState
 import com.google.samples.apps.nowinandroid.core.ui.NewsFeedUiState.Loading
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.filterNot
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onStart
-import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 
 @HiltViewModel
@@ -44,11 +43,7 @@ class BookmarksViewModel @Inject constructor(
         .map { newsResources -> newsResources.filter(SaveableNewsResource::isSaved) } // Only show bookmarked news resources.
         .map<List<SaveableNewsResource>, NewsFeedUiState>(NewsFeedUiState::Success)
         .onStart { emit(Loading) }
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5_000),
-            initialValue = Loading
-        )
+        .stateInScope(viewModelScope, initialValue = Loading)
 
     fun removeFromSavedResources(newsResourceId: String) {
         viewModelScope.launch {

feature/foryou/src/main/java/com/google/samples/apps/nowinandroid/feature/foryou/ForYouViewModel.kt

@@ -25,17 +25,16 @@ import com.google.samples.apps.nowinandroid.core.domain.GetSaveableNewsResources
 import com.google.samples.apps.nowinandroid.core.domain.GetSortedFollowableAuthorsStreamUseCase
 import com.google.samples.apps.nowinandroid.core.domain.model.SaveableNewsResource
 import com.google.samples.apps.nowinandroid.core.ui.NewsFeedUiState
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onStart
-import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 
 @HiltViewModel
@@ -50,12 +49,9 @@ class ForYouViewModel @Inject constructor(
     private val shouldShowOnboarding: Flow<Boolean> =
         userDataRepository.userDataStream.map { !it.shouldHideOnboarding }
 
-    val isSyncing = syncStatusMonitor.isSyncing
-        .stateIn(
-            scope = viewModelScope,
-            started = SharingStarted.WhileSubscribed(5_000),
-            initialValue = false
-        )
+    val isSyncing = syncStatusMonitor
+        .isSyncing
+        .stateInScope(viewModelScope, initialValue = false)
 
     val feedState: StateFlow<NewsFeedUiState> =
         userDataRepository.userDataStream
@@ -79,11 +75,7 @@ class ForYouViewModel @Inject constructor(
             // As the selected topics and topic state changes, this will cancel the old feed
             // monitoring and start the new one.
             .flatMapLatest { it }
-            .stateIn(
-                scope = viewModelScope,
-                started = SharingStarted.WhileSubscribed(5_000),
-                initialValue = NewsFeedUiState.Loading
-            )
+            .stateInScope(viewModelScope, initialValue = NewsFeedUiState.Loading)
 
     val onboardingUiState: StateFlow<OnboardingUiState> =
         combine(
@@ -99,12 +91,7 @@ class ForYouViewModel @Inject constructor(
             } else {
                 OnboardingUiState.NotShown
             }
-        }
-            .stateIn(
-                scope = viewModelScope,
-                started = SharingStarted.WhileSubscribed(5_000),
-                initialValue = OnboardingUiState.Loading
-            )
+        }.stateInScope(viewModelScope, initialValue = OnboardingUiState.Loading)
 
     fun updateTopicSelection(topicId: String, isChecked: Boolean) {
         viewModelScope.launch {

feature/interests/src/main/java/com/google/samples/apps/nowinandroid/feature/interests/InterestsViewModel.kt

@@ -24,14 +24,13 @@ import com.google.samples.apps.nowinandroid.core.domain.GetSortedFollowableAutho
 import com.google.samples.apps.nowinandroid.core.domain.TopicSortField
 import com.google.samples.apps.nowinandroid.core.domain.model.FollowableAuthor
 import com.google.samples.apps.nowinandroid.core.domain.model.FollowableTopic
+import com.google.samples.apps.nowinandroid.core.ui.stateInScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.combine
-import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 
@@ -54,11 +53,7 @@ class InterestsViewModel @Inject constructor(
         getSortedFollowableAuthorsStream(),
         getFollowableTopicsStream(sortBy = TopicSortField.NAME),
         InterestsUiState::Interests
-    ).stateIn(
-        scope = viewModelScope,
-        started = SharingStarted.WhileSubscribed(5_000),
-        initialValue = InterestsUiState.Loading
-    )
+    ).stateInScope(viewModelScope, initialValue = InterestsUiState.Loading)
 
     fun followTopic(followedTopicId: String, followed: Boolean) {
         viewModelScope.launch {