use less reflection in command line method invocation

api_params.go

@@ -56,13 +56,13 @@ type APIContainers struct {
 
 func (self *APIContainers) ToLegacy() APIContainersOld {
 	return APIContainersOld{
-		ID: self.ID,
-		Image: self.Image,
-		Command: self.Command,
-		Created: self.Created,
-		Status: self.Status,
-		Ports: displayablePorts(self.Ports),
-		SizeRw: self.SizeRw,
+		ID:         self.ID,
+		Image:      self.Image,
+		Command:    self.Command,
+		Created:    self.Created,
+		Status:     self.Status,
+		Ports:      displayablePorts(self.Ports),
+		SizeRw:     self.SizeRw,
 		SizeRootFs: self.SizeRootFs,
 	}
 }

api_test.go

@@ -566,7 +566,6 @@ func TestPostCommit(t *testing.T) {
 
 	srv := &Server{runtime: runtime}
 
-
 	// Create a container and remove a file
 	container, err := runtime.Create(
 		&Config{

commands.go

@@ -36,9 +36,13 @@ var (
 	VERSION   string
 )
 
-func (cli *DockerCli) getMethod(name string) (reflect.Method, bool) {
+func (cli *DockerCli) getMethod(name string) (func(...string) error, bool) {
 	methodName := "Cmd" + strings.ToUpper(name[:1]) + strings.ToLower(name[1:])
-	return reflect.TypeOf(cli).MethodByName(methodName)
+	method := reflect.ValueOf(cli).MethodByName(methodName)
+	if !method.IsValid() {
+		return nil, false
+	}
+	return method.Interface().(func(...string) error), true
 }
 
 func ParseCommands(proto, addr string, args ...string) error {
@@ -50,14 +54,7 @@ func ParseCommands(proto, addr string, args ...string) error {
 			fmt.Println("Error: Command not found:", args[0])
 			return cli.CmdHelp(args[1:]...)
 		}
-		ret := method.Func.CallSlice([]reflect.Value{
-			reflect.ValueOf(cli),
-			reflect.ValueOf(args[1:]),
-		})[0].Interface()
-		if ret == nil {
-			return nil
-		}
-		return ret.(error)
+		return method(args[1:]...)
 	}
 	return cli.CmdHelp(args...)
 }
@@ -68,10 +65,7 @@ func (cli *DockerCli) CmdHelp(args ...string) error {
 		if !exists {
 			fmt.Fprintf(cli.err, "Error: Command not found: %s\n", args[0])
 		} else {
-			method.Func.CallSlice([]reflect.Value{
-				reflect.ValueOf(cli),
-				reflect.ValueOf([]string{"--help"}),
-			})[0].Interface()
+			method("--help")
 			return nil
 		}
 	}