Merge pull request #2 from cheonjaewoong/nullable-notnull-property

Add not-null property delegate

savedstate-ktx/src/androidTest/AndroidManifest.xml

@@ -3,6 +3,7 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="io.woong.savedstate.test">
     <application>
-        <activity android:name="io.woong.savedstate.PropertyDelegatorTest$TestActivity" />
+        <activity android:name="io.woong.savedstate.NullablePropertyDelegatorTest$TestActivity" />
+        <activity android:name="io.woong.savedstate.NotNullPropertyDelegatorTest$TestActivity" />
     </application>
 </manifest>

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

@@ -0,0 +1,64 @@
+package io.woong.savedstate
+
+import android.content.Context
+import androidx.activity.ComponentActivity
+import androidx.activity.viewModels
+import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModel
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.core.app.launchActivity
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.google.common.truth.Truth.assertThat
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+public class NotNullPropertyDelegatorTest {
+    private lateinit var context: Context
+
+    @Before
+    public fun init() {
+        context = ApplicationProvider.getApplicationContext()
+    }
+
+    @Test
+    public fun notNullWithInitialValue() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            assertThat(viewModel.notNullValue).isEqualTo("a")
+            assertThat(viewModel.notNullVariable).isEqualTo("b")
+
+            viewModel.notNullVariable = "c"
+            assertThat(viewModel.notNullVariable).isEqualTo("c")
+        }
+    }
+
+    @Test
+    public fun stateSaving() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            viewModel.notNullVariable = "bbb"
+
+            assertThat(viewModel.notNullValue).isEqualTo("a")
+            assertThat(viewModel.notNullVariable).isEqualTo("bbb")
+        }
+        scenario.recreate()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            assertThat(viewModel.notNullValue).isEqualTo("a")
+            assertThat(viewModel.notNullVariable).isEqualTo("bbb")
+        }
+    }
+
+    public class TestActivity : ComponentActivity() {
+        public val viewModel: TestViewModel by viewModels()
+    }
+
+    public class TestViewModel(savedStateHandle: SavedStateHandle) : ViewModel() {
+        public val notNullValue: String by savedStateHandle.notNull("a")
+        public var notNullVariable: String by savedStateHandle.notNull("b")
+    }
+}

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

@@ -0,0 +1,85 @@
+package io.woong.savedstate
+
+import android.content.Context
+import androidx.activity.ComponentActivity
+import androidx.activity.viewModels
+import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModel
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.core.app.launchActivity
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.google.common.truth.Truth.assertThat
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+public class NullablePropertyDelegatorTest {
+    private lateinit var context: Context
+
+    @Before
+    public fun init() {
+        context = ApplicationProvider.getApplicationContext()
+    }
+
+    @Test
+    public fun simplestDelegate() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            assertThat(viewModel.simpleValue).isNull()
+            assertThat(viewModel.simpleVariable).isNull()
+
+            viewModel.simpleVariable = "test"
+            assertThat(viewModel.simpleVariable).isEqualTo("test")
+        }
+    }
+
+    @Test
+    public fun nullableWithInitialValue() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            assertThat(viewModel.initializedValue).isEqualTo("a")
+            assertThat(viewModel.initializedVariable).isEqualTo("b")
+
+            viewModel.initializedVariable = "c"
+            assertThat(viewModel.initializedVariable).isEqualTo("c")
+        }
+    }
+
+    @Test
+    public fun stateSaving() {
+        val scenario = launchActivity<TestActivity>()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            viewModel.simpleVariable = "aaa"
+            viewModel.initializedVariable = "bbb"
+
+            assertThat(viewModel.simpleValue).isNull()
+            assertThat(viewModel.simpleVariable).isEqualTo("aaa")
+            assertThat(viewModel.initializedValue).isEqualTo("a")
+            assertThat(viewModel.initializedVariable).isEqualTo("bbb")
+        }
+        scenario.recreate()
+        scenario.onActivity { activity ->
+            val viewModel = activity.viewModel
+            assertThat(viewModel.simpleValue).isNull()
+            assertThat(viewModel.simpleVariable).isEqualTo("aaa")
+            assertThat(viewModel.initializedValue).isEqualTo("a")
+            assertThat(viewModel.initializedVariable).isEqualTo("bbb")
+        }
+    }
+
+    public class TestActivity : ComponentActivity() {
+        public val viewModel: TestViewModel by viewModels()
+    }
+
+    public class TestViewModel(savedStateHandle: SavedStateHandle) : ViewModel() {
+        public val simpleValue: String? by savedStateHandle
+        public var simpleVariable: String? by savedStateHandle
+
+        public val initializedValue: String? by savedStateHandle.nullable("a")
+        public var initializedVariable: String? by savedStateHandle.nullable("b")
+    }
+}

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

@@ -0,0 +1,62 @@
+package io.woong.savedstate
+
+import androidx.lifecycle.SavedStateHandle
+import kotlin.reflect.KProperty
+
+/**
+ * Returns a property delegate for reading and writing a not-null value into [SavedStateHandle]
+ * with initial value.
+ *
+ * Reading the property equals to read value from [SavedStateHandle]
+ * and writing equals to write value to [SavedStateHandle].
+ *
+ * To define not-null property delegate, use `by` keyword of Kotlin:
+ * The property must not-null type.
+ *
+ * ```
+ * class ExampleViewModel(savedStateHandle: SavedStateHandle) {
+ *     // This code equals to below code:
+ *     // var foo: String
+ *     //     get() = savedStateHandle["foo"]!!
+ *     //     set(value) { savedStateHandle["foo"] = value }
+ *     //
+ *     // init {
+ *     //     if (!savedStateHandle.contains("foo")) {
+ *     //         savedStateHandle["foo"] = "init"
+ *     //     }
+ *     // }
+ *     var foo: String by savedStateHandle.notNull("init")
+ * }
+ * ```
+ *
+ * @param initialValue The initial value of this property.
+ */
+public fun <T> SavedStateHandle.notNull(initialValue: T): NotNullPropertyDelegateProvider<T> {
+    return NotNullPropertyDelegateProvider(savedStateHandle = this, initialValue)
+}
+
+public class NotNullPropertyDelegateProvider<T>(
+    private val savedStateHandle: SavedStateHandle,
+    private val initialValue: T
+) {
+    public operator fun provideDelegate(self: Any?, property: KProperty<*>): NotNullPropertyDelegate<T> {
+        val key = property.name
+        if (!savedStateHandle.contains(key)) {
+            savedStateHandle[key] = initialValue
+        }
+        return NotNullPropertyDelegate(savedStateHandle, key)
+    }
+}
+
+public class NotNullPropertyDelegate<T>(
+    private val savedStateHandle: SavedStateHandle,
+    private val key: String
+) {
+    public operator fun getValue(self: Any?, property: KProperty<*>): T {
+        return savedStateHandle[key]!!
+    }
+
+    public operator fun setValue(self: Any?, property: KProperty<*>, value: T) {
+        savedStateHandle[key] = value
+    }
+}