alsa: Use ? operator instead of and_then

src/widgets/audio/alsa_sound.rs

@@ -1,4 +1,3 @@
-
 use crate::color::Color;
 use crate::widgets::bar_widget::{BarWidget, BarWidgetImpl};
 
@@ -12,7 +11,10 @@ const SELEM_ID: u32 = 0u32;
 fn alsa_error_to_io_error(fail: &'static str, err: &alsa::Error) -> ::std::io::Error {
     let kind = ::std::io::ErrorKind::Other;
     let func = err.func();
-    let errno = err.errno().map(|errno| format!("; errno = {}", errno)).unwrap_or(String::new());
+    let errno = err
+        .errno()
+        .map(|errno| format!("; errno = {}", errno))
+        .unwrap_or(String::new());
     return ::std::io::Error::new(kind, format!("{}: {}{}", fail, func, errno));
 }
 
@@ -51,35 +53,32 @@ impl Alsa {
         }
     }
     pub fn get_master_volume(&self) -> ::std::io::Result<f32> {
-        self.get_master()
+        let master = self.get_master()?;
-            .and_then(|master| {
         let (min, max) = master.get_playback_volume_range();
-                master.get_playback_volume(SelemChannelId::mono())
+        master
+            .get_playback_volume(SelemChannelId::mono())
             .map(|volume| alsa_volume_to_f32(volume, min, max))
             .map_err(|e| alsa_error_to_io_error("Failed to get `Master` volume", &e))
-            })
     }
     pub fn set_master_volume(&self, volume: f32) -> ::std::io::Result<()> {
-        self.get_master()
+        let master = self.get_master()?;
-            .and_then(|master| {
         let (min, max) = master.get_playback_volume_range();
         let volume = f32_to_alsa_volume(volume, min, max);
-                master.set_playback_volume_all(volume)
+        master
+            .set_playback_volume_all(volume)
             .map_err(|e| alsa_error_to_io_error("Failed to set `Master` volume", &e))
-            })
     }
     pub fn inc_master_volume(&self, diff: f32) -> ::std::io::Result<()> {
-        self.get_master()
+        let master = self.get_master()?;
-            .and_then(|master| {
         let (min, max) = master.get_playback_volume_range();
-                master.get_playback_volume(SelemChannelId::mono())
+        master
+            .get_playback_volume(SelemChannelId::mono())
             .and_then(|volume| {
                 let volume = alsa_volume_to_f32(volume, min, max);
                 let volume = f32_to_alsa_volume(volume + diff, min, max);
                 master.set_playback_volume_all(volume)
             })
             .map_err(|e| alsa_error_to_io_error("Failed to inc/dec `Master` volume", &e))
-            })
     }
 }
 
@@ -90,7 +89,7 @@ impl BarWidgetImpl for Alsa {
     fn value(&self) -> f32 {
         match self.get_master_volume() {
             Ok(v) => v,
-            Err(e) => panic!(e)
+            Err(e) => panic!(e),
         }
     }
     fn color(&self) -> Color {