Merge pull request #88 from trntv/master

Pre- and Post- update functions

spinner.go

@@ -183,6 +183,8 @@ type Spinner struct {
 	active     bool                          // active holds the state of the spinner
 	stopChan   chan struct{}                 // stopChan is a channel used to stop the indicator
 	HideCursor bool                          // hideCursor determines if the cursor is visible
+	PreUpdate  func(s *Spinner)              // will be triggered before every spinner update
+	PostUpdate func(s *Spinner)              // will be triggered after every spinner update
 }
 
 // New provides a pointer to an instance of Spinner with the supplied options
@@ -278,6 +280,10 @@ func (s *Spinner) Start() {
 						return
 					}
 
+					if s.PreUpdate != nil {
+						s.PreUpdate(s)
+					}
+
 					var outColor string
 					if runtime.GOOS == "windows" {
 						if s.Writer == os.Stderr {
@@ -292,8 +298,12 @@ func (s *Spinner) Start() {
 					fmt.Fprint(s.Writer, outColor)
 					s.lastOutput = outPlain
 					delay := s.Delay
-					s.lock.Unlock()
 
+					if s.PostUpdate != nil {
+						s.PostUpdate(s)
+					}
+
+					s.lock.Unlock()
 					time.Sleep(delay)
 				}
 			}

spinner_test.go

@@ -126,6 +126,36 @@ func TestRestart(t *testing.T) {
 	s = nil
 }
 
+// TestHookFunctions will verify that hook functions works as expected
+func TestHookFunctions(t *testing.T) {
+	s := New(CharSets[4], 50*time.Millisecond)
+	var out syncBuffer
+	s.Writer = &out
+	s.PreUpdate = func(s *Spinner) {
+		fmt.Fprintf(s.Writer, "pre-update")
+	}
+	s.PostUpdate = func(s *Spinner) {
+		fmt.Fprintf(s.Writer, "post-update")
+	}
+
+	s.Start()
+	s.Color("cyan")
+	time.Sleep(200 * time.Millisecond)
+	s.Stop()
+	time.Sleep(50 * time.Millisecond)
+	out.Lock()
+	defer out.Unlock()
+	result := out.Bytes()
+	if !bytes.Contains(result, []byte("pre-update")) {
+		t.Error("pre-update failed")
+	}
+
+	if !bytes.Contains(result, []byte("post-update")) {
+		t.Error("post-update failed")
+	}
+	s = nil
+}
+
 // TestReverse will verify that the given spinner can stop and start again reversed
 func TestReverse(t *testing.T) {
 	a := New(CharSets[10], 1*time.Second)