swiftui : enable stream updating (#7754)

Author: shu223

examples/llama.swiftui/llama.swiftui/Models/LlamaState.swift

@@ -131,22 +131,29 @@ class LlamaState: ObservableObject {
 
         messageLog += "\(text)"
 
-        while await llamaContext.n_cur < llamaContext.n_len {
-            let result = await llamaContext.completion_loop()
-            messageLog += "\(result)"
-        }
+        Task.detached {
+            while await llamaContext.n_cur < llamaContext.n_len {
+                let result = await llamaContext.completion_loop()
+                await MainActor.run {
+                    self.messageLog += "\(result)"
+                }
+            }
 
-        let t_end = DispatchTime.now().uptimeNanoseconds
-        let t_generation = Double(t_end - t_heat_end) / NS_PER_S
-        let tokens_per_second = Double(await llamaContext.n_len) / t_generation
+            let t_end = DispatchTime.now().uptimeNanoseconds
+            let t_generation = Double(t_end - t_heat_end) / self.NS_PER_S
+            let tokens_per_second = Double(await llamaContext.n_len) / t_generation
 
-        await llamaContext.clear()
-        messageLog += """
-            \n
-            Done
-            Heat up took \(t_heat)s
-            Generated \(tokens_per_second) t/s\n
-            """
+            await llamaContext.clear()
+
+            await MainActor.run {
+                self.messageLog += """
+                    \n
+                    Done
+                    Heat up took \(t_heat)s
+                    Generated \(tokens_per_second) t/s\n
+                    """
+            }
+        }
     }
 
     func bench() async {