Merge branch 'frontend/launch-catching' into 'main'

feat: added a launchCatching

See merge request EmmaVandewalle/writand!34

app/src/main/java/be/re/writand/screens/WViewModel.kt

@@ -0,0 +1,41 @@
+package be.re.writand.screens
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import be.re.writand.utils.SnackbarManager
+import be.re.writand.utils.SnackbarMessage.Companion.toSnackbarMessage
+import kotlinx.coroutines.CoroutineExceptionHandler
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
+
+/**
+ * Custom viewmodel class for this app.
+ */
+class WViewModel : ViewModel() {
+
+    /**
+     * Function to launch a suspended function in viewmodel scope.
+     * This function catches possible errors and displays them as a snackbar message.
+     * @param[snackbar] controls if a snackbar must be shown or not.
+     * @param[finally] a lambda-function to execute after the [block] is executed.
+     * @param[block] the code that must be executed in a Coroutine-context.
+     */
+    fun launchCatching(
+        snackbar: Boolean = true,
+        finally: () -> Unit = {},
+        block: suspend CoroutineScope.() -> Unit
+    ) =
+        viewModelScope.launch(
+            CoroutineExceptionHandler { _, throwable ->
+                finally()
+                if (snackbar) {
+                    SnackbarManager.showMessage(throwable.toSnackbarMessage())
+                }
+            },
+            block = {
+                block()
+                finally()
+            }
+        )
+
+}

app/src/main/java/be/re/writand/utils/SnackbarManager.kt

@@ -0,0 +1,43 @@
+package be.re.writand.utils
+
+import be.re.writand.utils.SnackbarMessage.Companion.toSnackbarMessage
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+
+/**
+ * Represents a message to be shown inside a snackbar.
+ */
+sealed class SnackbarMessage {
+    class StringSnackbar(val message: String) : SnackbarMessage()
+
+    companion object {
+
+        fun Throwable.toSnackbarMessage(): String {
+            return this.message.orEmpty()
+        }
+
+        fun SnackbarMessage.toMessage(): String {
+            return when (this) {
+                is StringSnackbar -> this.message
+            }
+        }
+    }
+}
+
+/**
+ * The actual manager of the snackbar's messages.
+ */
+object SnackbarManager {
+    private val messages: MutableStateFlow<SnackbarMessage?> = MutableStateFlow(null)
+    val snackbarMessages: StateFlow<SnackbarMessage?>
+        get() = messages.asStateFlow()
+
+    fun showMessage(message: String) {
+        messages.value = SnackbarMessage.StringSnackbar(message)
+    }
+
+    fun showMessage(message: Throwable) {
+        messages.value = SnackbarMessage.StringSnackbar(message.toSnackbarMessage())
+    }
+}