Renamed from to cast_mut and added version that is not mutable

src/devices.rs

@@ -7,23 +7,35 @@ use crate::{mqtt::Listener, state::StateOnOff};
 pub use self::ikea_outlet::IkeaOutlet;
 
 pub trait AsListener {
-    fn from(&mut self) -> Option<&mut dyn Listener> {
+    fn cast(&self) -> Option<&dyn Listener> {
+        None
+    }
+    fn cast_mut(&mut self) -> Option<&mut dyn Listener> {
         None
     }
 }
 impl<T: Device + Listener> AsListener for T {
-    fn from(&mut self) -> Option<&mut dyn Listener> {
+    fn cast(&self) -> Option<&dyn Listener> {
+        Some(self)
+    }
+    fn cast_mut(&mut self) -> Option<&mut dyn Listener> {
         Some(self)
     }
 }
 
 pub trait AsStateOnOff {
-    fn from(&mut self) -> Option<&mut dyn StateOnOff> {
+    fn cast(&self) -> Option<&dyn StateOnOff> {
+        None
+    }
+    fn cast_mut(&mut self) -> Option<&mut dyn StateOnOff> {
         None
     }
 }
 impl<T: Device + StateOnOff> AsStateOnOff for T {
-    fn from(&mut self) -> Option<&mut dyn StateOnOff> {
+    fn cast(&self) -> Option<&dyn StateOnOff> {
+        Some(self)
+    }
+    fn cast_mut(&mut self) -> Option<&mut dyn StateOnOff> {
         Some(self)
     }
 }
@@ -46,7 +58,7 @@ impl Devices {
     }
 
     pub fn get_listeners(&mut self) -> Vec<&mut dyn Listener> {
-        self.devices.iter_mut().filter_map(|(_, device)| AsListener::from(device.as_mut())).collect()
+        self.devices.iter_mut().filter_map(|(_, device)| AsListener::cast_mut(device.as_mut())).collect()
     }
 
     pub fn get_device(&mut self, name: &str) -> Option<&mut dyn Device> {

src/main.rs

@@ -35,7 +35,7 @@ fn main() {
     let mut notifier = Notifier::new();
 
     // Update the state of the kettle
-    AsStateOnOff::from(devices.borrow_mut().get_device("kitchen/kettle").unwrap()).unwrap().set_state(false);
+    AsStateOnOff::cast_mut(devices.borrow_mut().get_device("kitchen/kettle").unwrap()).unwrap().set_state(false);
 
     notifier.add_listener(Rc::downgrade(&devices));