Merge pull request #12 from cheonjaewoong/mutablestateflow

Add new feature, `SavedStateHandle.mutableStateFlow`

README.md

@@ -1,7 +1,8 @@
 # SavedState KTX
 
-![maven-central](https://img.shields.io/maven-central/v/io.woong.savedstate/savedstate-ktx)
+![android-sdk](https://img.shields.io/badge/android-21+-brightgreen?logo=android)
 ![kotlin-version](https://img.shields.io/badge/kotlin-1.7.20-blueviolet?logo=kotlin)
+![maven-central](https://img.shields.io/maven-central/v/io.woong.savedstate/savedstate-ktx)
 ![license](https://img.shields.io/badge/license-MIT-blue)
 [![test](https://github.com/cheonjaewoong/savedstate-ktx/actions/workflows/test.yaml/badge.svg)](https://github.com/cheonjaewoong/savedstate-ktx/actions/workflows/test.yaml)
 
@@ -70,6 +71,16 @@ class SampleViewModel(savedStateHandle: SavedStateHandle) : ViewModel() {
 
 Like delegated livedata, you can use delegated stateflow like this.
 
+```kotlin
+class SampleViewModel(savedStateHandle: SavedStateHandle) : ViewModel() {
+    @OptIn(ExperimentalSavedStateKtxApi::class)
+    val stateFlow: MutableStateFlow<String> by savedStateHandle.mutableStateFlow("init")
+}
+```
+
+Delegated mutable stateflow is currently experimental feature.
+You can use like above sample.
+
 ## License
 
-SavedState KTX is published under the [MIT License](./LICENSE.txt).
+SavedState KTX is under the [MIT License](./LICENSE.txt).

savedstate-ktx/build.gradle.kts

@@ -36,7 +36,6 @@ dependencies {
     androidTestImplementation("androidx.test.ext:junit-ktx:1.1.5")
     androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
     androidTestImplementation("com.google.truth:truth:1.1.3")
-    androidTestImplementation("androidx.appcompat:appcompat:1.5.1")
     androidTestImplementation("androidx.activity:activity-ktx:1.6.1")
 }
 

savedstate-ktx/src/androidTest/java/io/woong/savedstate/DelegatedStateFlowTest.kt

@@ -4,17 +4,19 @@ import androidx.activity.ComponentActivity
 import androidx.activity.viewModels
 import androidx.lifecycle.SavedStateHandle
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
 import androidx.test.core.app.launchActivity
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.google.common.truth.Truth.assertThat
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.junit.Test
 import org.junit.runner.RunWith
 
 @RunWith(AndroidJUnit4::class)
 public class DelegatedStateFlowTest {
     @Test
-    public fun savedStateDelegate() {
+    public fun stateFlowDelegate() {
         val scenario = launchActivity<TestActivity>()
         scenario.onActivity { activity ->
             val viewModel = activity.viewModel
@@ -24,12 +26,42 @@ public class DelegatedStateFlowTest {
                 viewModel.savedStateHandle.get<String>("stateFlow")
             ).isEqualTo("init")
 
-            viewModel.savedStateHandle["stateFlow"] = "new"
+            viewModel.savedStateHandle["stateFlow"] = "first"
+            assertThat(viewModel.stateFlow.value).isEqualTo("first")
+            assertThat(
+                viewModel.savedStateHandle.get<String>("stateFlow")
+            ).isEqualTo("first")
 
-            assertThat(viewModel.stateFlow.value).isEqualTo("new")
+            viewModel.savedStateHandle["stateFlow"] = "second"
+            assertThat(viewModel.stateFlow.value).isEqualTo("second")
             assertThat(
                 viewModel.savedStateHandle.get<String>("stateFlow")
-            ).isEqualTo("new")
+            ).isEqualTo("second")
+        }
+    }
+
+    @Test
+    public fun mutableStateFlowDelegate() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+
+            assertThat(viewModel.mutableStateFlow.value).isEqualTo("init")
+            assertThat(
+                viewModel.savedStateHandle.get<String>("mutableStateFlow")
+            ).isEqualTo("init")
+
+            viewModel.mutableStateFlow.value = "first"
+            assertThat(viewModel.mutableStateFlow.value).isEqualTo("first")
+            assertThat(
+                viewModel.savedStateHandle.get<String>("mutableStateFlow")
+            ).isEqualTo("first")
+
+            viewModel.mutableStateFlow.value = "second"
+            assertThat(viewModel.mutableStateFlow.value).isEqualTo("second")
+            assertThat(
+                viewModel.savedStateHandle.get<String>("mutableStateFlow")
+            ).isEqualTo("second")
         }
     }
 
@@ -39,5 +71,9 @@ public class DelegatedStateFlowTest {
 
     public class TestViewModel(public val savedStateHandle: SavedStateHandle) : ViewModel() {
         public val stateFlow: StateFlow<String> by savedStateHandle.stateFlow("init")
+
+        @OptIn(ExperimentalSavedStateKtxApi::class)
+        public val mutableStateFlow: MutableStateFlow<String>
+            by savedStateHandle.mutableStateFlow("init", viewModelScope)
     }
 }

savedstate-ktx/src/main/java/io/woong/savedstate/DelegatedStateFlow.kt

@@ -1,7 +1,12 @@
 package io.woong.savedstate
 
+import androidx.lifecycle.Observer
 import androidx.lifecycle.SavedStateHandle
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.onCompletion
+import kotlinx.coroutines.launch
 import kotlin.reflect.KProperty
 
 /**
@@ -13,6 +18,20 @@ public fun <T> SavedStateHandle.stateFlow(initialValue: T): StateFlowDelegatePro
     return StateFlowDelegateProvider(savedStateHandle = this, initialValue)
 }
 
+/**
+ * Returns a delegated [MutableStateFlow] that hande value stored in the [SavedStateHandle].
+ *
+ * @param initialValue Initial value of this [MutableStateFlow].
+ * @param coroutineScope A [CoroutineScope] to control [MutableStateFlow].
+ */
+@ExperimentalSavedStateKtxApi
+public fun <T> SavedStateHandle.mutableStateFlow(
+    initialValue: T,
+    coroutineScope: CoroutineScope
+): MutableStateFlowDelegateProvider<T> {
+    return MutableStateFlowDelegateProvider(savedStateHandle = this, initialValue, coroutineScope)
+}
+
 /**
  * Internal delegated [StateFlow] provider.
  */
@@ -43,3 +62,59 @@ public class DelegatedStateFlow<T>(
         return stateFlow
     }
 }
+
+/**
+ * Internal delegated [MutableStateFlow] provider.
+ */
+@ExperimentalSavedStateKtxApi
+public class MutableStateFlowDelegateProvider<T>(
+    private val savedStateHandle: SavedStateHandle,
+    private val initialValue: T,
+    private val coroutineScope: CoroutineScope
+) {
+    public operator fun provideDelegate(
+        self: Any?,
+        property: KProperty<*>
+    ): DelegatedMutableStateFlow<T> {
+        val key = property.name
+        return DelegatedMutableStateFlow(savedStateHandle, key, initialValue, coroutineScope)
+    }
+}
+
+/**
+ * Internal implementation of delegated [MutableStateFlow].
+ */
+@ExperimentalSavedStateKtxApi
+public class DelegatedMutableStateFlow<T>(
+    savedStateHandle: SavedStateHandle,
+    key: String,
+    initialValue: T,
+    coroutineScope: CoroutineScope
+) {
+    private val mutableStateFlow: MutableStateFlow<T>
+
+    init {
+        val liveData = savedStateHandle.getLiveData(key, initialValue)
+        val stateFlow = MutableStateFlow(initialValue)
+        val observer = Observer<T?> { value ->
+            if (value != stateFlow.value) {
+                stateFlow.value = value
+            }
+        }
+        liveData.observeForever(observer)
+        coroutineScope.launch {
+            stateFlow.onCompletion {
+                liveData.removeObserver(observer)
+            }.collect { value ->
+                if (value != liveData.value) {
+                    liveData.value = value
+                }
+            }
+        }
+        mutableStateFlow = stateFlow
+    }
+
+    public operator fun getValue(self: Any?, property: KProperty<*>): MutableStateFlow<T> {
+        return mutableStateFlow
+    }
+}

savedstate-ktx/src/main/java/io/woong/savedstate/ExperimentalSavedStateKtxApi.kt

@@ -0,0 +1,11 @@
+package io.woong.savedstate
+
+/**
+ * Marker for experimental features of `savedstate-ktx` library.
+ */
+@RequiresOptIn(
+    message = "This is experimental API. It could be removed or changed in the future.",
+    level = RequiresOptIn.Level.ERROR
+)
+@Retention(AnnotationRetention.BINARY)
+public annotation class ExperimentalSavedStateKtxApi