the voices::Backend trait is almost stable

src/backends/av_foundation.rs

@@ -101,7 +101,7 @@ impl AvFoundation {
                 rate: 0.5,
                 volume: 1.,
                 pitch: 1.,
-                voice: AVSpeechSynthesisVoice::new(""),
+                voice: AVSpeechSynthesisVoice::new(),
             }
         };
         *backend_id += 1;
@@ -231,7 +231,7 @@ impl Backend for AvFoundation {
     }
 
     fn set_voice(&mut self, voice: &str) -> Result<(),Error> {
-        self.voice = AVSpeechSynthesisVoice::new(voice);
+        self.voice = AVSpeechSynthesisVoice::new();
         Ok(())
     }
 }

src/backends/av_foundation/voices.rs

@@ -14,11 +14,10 @@ use crate::voices::Gender;
 pub(crate) struct AVSpeechSynthesisVoice(*const Object);
 
 impl AVSpeechSynthesisVoice {
-    pub fn new(identifier: &str) -> Self {
+    pub fn new() -> Self {
         let voice: *const Object;
         unsafe{
-            let i: id = NSString::alloc(nil).init_str(identifier);
+            voice = msg_send![class!(AVSpeechSynthesisVoice), new];
-            voice = msg_send![class!(AVSpeechSynthesisVoice), voiceWithIdentifier:i];
         };
         AVSpeechSynthesisVoice{0:voice}
     }
@@ -27,6 +26,14 @@ impl AVSpeechSynthesisVoice {
 impl voices::Backend for AVSpeechSynthesisVoice {
     type Backend = AvFoundation;
 
+    fn from_id(id: String) -> Self {
+        unimplemented!()
+    }
+
+    fn from_language(lang: voices::LanguageIdentifier) -> Self {
+        unimplemented!()
+    }
+
     fn list() -> Vec<Self> {
         let voices: CFArray = unsafe{msg_send![class!(AVSpeechSynthesisVoice), speechVoices]};
         voices.iter().map(|v| {

src/voices.rs

@@ -9,9 +9,13 @@ pub enum Gender {
 
 pub trait Backend: Sized {
     type Backend: crate::Backend;
+    fn from_id(id: String) -> Self;
+    fn from_language(lang: LanguageIdentifier) -> Self;
     fn list() -> Vec<Self>;
     fn name(self) -> String;
     fn gender(self) -> Gender;
     fn id(self) -> String;
     fn language(self) -> LanguageIdentifier;
 }
+
+pub struct Voice<T: Backend + Sized>(Box<T>);