use right var

mpc_shim.rb

@@ -1,51 +1,51 @@
 class MpcShim
   def update()
-    `mpc #{host_arg} update`
+    `mpc #{@host_arg} update`
   end
 
   def clear()
-    `mpc #{host_arg} clear`
+    `mpc #{@host_arg} clear`
   end
 
   def play()
-    `mpc #{host_arg} play`
+    `mpc #{@host_arg} play`
   end
 
   def stop()
-    `mpc #{host_arg} stop`
+    `mpc #{@host_arg} stop`
   end
 
   def next()
-    `mpc #{host_arg} next`
+    `mpc #{@host_arg} next`
   end
 
   def reset()
-    `mpc #{host_arg} clear`
-    `mpc #{host_arg} add /`
-    `mpc #{host_arg} shuffle`
-    `mpc #{host_arg} repeat`
+    `mpc #{@host_arg} clear`
+    `mpc #{@host_arg} add /`
+    `mpc #{@host_arg} shuffle`
+    `mpc #{@host_arg} repeat`
   end
 
   def update()
-    `mpc #{host_arg} update`
+    `mpc #{@host_arg} update`
   end
 
   def toggle()
-    `mpc #{host_arg} toggle`
+    `mpc #{@host_arg} toggle`
   end
 
   def add(filename = nil)
     if filename == nil
-      `mpc #{host_arg} add /`
+      `mpc #{@host_arg} add /`
     else
-      `mpc #{host_arg} add #{filename}`
+      `mpc #{@host_arg} add #{filename}`
     end
     return $?.success?
   end
 
   def start()
     `systemctl start mpd` unless `ps aux | grep mpd` != ""
-    `mpc ${host_arg} repeat`
+    `mpc ${@host_arg} repeat`
   end
 
   def running?()
@@ -53,7 +53,7 @@ class MpcShim
   end
 
   def nowplaying()
-    return `mpc ${host_arg} | head -n 1`
+    return `mpc ${@host_arg} | head -n 1`
   end
 
   def initialize(hostname=:localhost)