Making Entry struct for StateStorage

iced-rs · Sep 26, 2021 · 17832e1 · 17832e1
1 parent 68e5df6
commit 17832e1
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Showing 3 changed files with 56 additions and 18 deletions.
diff --git a/examples/todos/src/main.rs b/examples/todos/src/main.rs
@@ -101,9 +101,10 @@ impl Application for Todos {
                     }
                     Message::TaskMessage(i, task_message) => {
                         if let Some(task) = state.tasks.get_mut(i) {
-                            states.enter(&format!("task_{}", i));
-                            task.update(task_message, states);
-                            states.exit();
+                            task.update(
+                                task_message, 
+                                &mut states.enter(&format!("task_{}", i))
+                            );
                         }
                     }
                     Message::Saved(_) => {

diff --git a/native/src/element.rs b/native/src/element.rs
@@ -268,22 +268,18 @@ where
     /// Making State Array of Widget for saving
     pub fn into_states(self, hash: Hasher, states: &mut StateStorage) {
         if let Some(id) = &self.root_id {
-            states.enter(&id);
-        }
-        self.widget.into_states(hash, states);
-        if self.root_id.is_some() {
-            states.exit();
+            self.widget.into_states(hash, &mut states.enter(&id));
+        } else {
+            self.widget.into_states(hash, states);
         }
     }
 
     /// Apply States for widget
     pub fn apply_states(&mut self, hash: Hasher, states: &mut StateStorage) {
         if let Some(id) = &self.root_id {
-            states.enter(&id);
-        }
-        self.widget.apply_states(hash, states);
-        if self.root_id.is_some() {
-            states.exit();
+            self.widget.apply_states(hash, &mut states.enter(&id));
+        } else {
+            self.widget.apply_states(hash, states);
         }
     }
 

diff --git a/native/src/state_storage.rs b/native/src/state_storage.rs
@@ -67,11 +67,52 @@ impl StateStorage {
     }
 
     /// Entering a state group
-    pub fn enter(&mut self, id: &str) {
-        self.path.push(id);
+    /// the function is called from [`Element`] and [`Application::update`]
+    pub fn enter(&mut self, id: &str) -> Entry<'_> {
+        Entry::new(self)
+            .enter(id)
     }
-    /// Exit from the group
-    pub fn exit(&mut self) {
-        let _ = self.path.pop();
+}
+
+/// Access to the state at a lower level
+/// This `struct` is constructed from the [`enter`] method on [`StateStorage`].
+#[derive(Debug)]
+pub struct Entry <'a> {
+    storage: &'a mut StateStorage,
+    is_enter: bool,
+}
+
+impl <'a> Entry<'a> {
+    fn new(storage: &'a mut StateStorage) -> Self {
+        Entry {
+            storage, 
+            is_enter: false,
+        }
+    }
+    fn enter(mut self, id: &str) -> Self {
+        self.storage.path.push(id);
+        self.is_enter = true;
+        self
+    }
+}
+
+impl <'a> Drop for Entry <'a> {
+    fn drop(&mut self) {
+        if self.is_enter {
+            let _ = self.path.pop();
+        }
+    }
+}
+
+impl <'a> std::ops::Deref for Entry<'a> {
+    type Target = StateStorage;
+    fn deref(&self) -> &StateStorage {
+        &self.storage
+    }
+}
+
+impl <'a> std::ops::DerefMut for Entry<'a> {
+    fn deref_mut(&mut self) -> &mut StateStorage {
+        &mut self.storage
     }
 }