Add example illustrating how to send messages via channels in realtime

examples/realtime/main.go

@@ -0,0 +1,92 @@
+package main
+
+// A simple example that shows how to send activity to Bubble Tea in real-time
+// through a channel.
+
+import (
+	"fmt"
+	"math/rand"
+	"os"
+	"time"
+
+	"github.com/charmbracelet/bubbles/spinner"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+// A message used to indicate that activity has occured. In the real world (for
+// example, chat) this would contain actual data.
+type responseMsg struct{}
+
+// Simulate a process that sends events at an irregular interval in real time.
+// In this case, we'll send events on the channel at a random interval between
+// 100 to 1000 milliseconds. As a command, Bubble Tea will run this
+// asyncronously.
+func listenForActivity(sub chan struct{}) tea.Cmd {
+	return func() tea.Msg {
+		for {
+			time.Sleep(time.Millisecond * time.Duration(rand.Int63n(900)+100))
+			sub <- struct{}{}
+		}
+	}
+}
+
+// A command that waits for the activity on a channel.
+func waitForActivity(sub chan struct{}) tea.Cmd {
+	return func() tea.Msg {
+		return responseMsg(<-sub)
+	}
+}
+
+type model struct {
+	sub       chan struct{} // where we'll receive activity notifications
+	responses int           // how many responses we've received
+	spinner   spinner.Model
+	quitting  bool
+}
+
+func (m model) Init() tea.Cmd {
+	return tea.Batch(
+		spinner.Tick,
+		listenForActivity(m.sub), // generate activity
+		waitForActivity(m.sub),   // wait for activity
+	)
+}
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg.(type) {
+	case tea.KeyMsg:
+		m.quitting = true
+		return m, tea.Quit
+	case responseMsg:
+		m.responses++                    // record external activity
+		return m, waitForActivity(m.sub) // wait for next event
+	case spinner.TickMsg:
+		var cmd tea.Cmd
+		m.spinner, cmd = m.spinner.Update(msg)
+		return m, cmd
+	default:
+		return m, nil
+	}
+}
+
+func (m model) View() string {
+	s := fmt.Sprintf("\n %s Events received: %d\n\n Press any key to exit\n", m.spinner.View(), m.responses)
+	if m.quitting {
+		s += "\n"
+	}
+	return s
+}
+
+func main() {
+	rand.Seed(time.Now().UTC().UnixNano())
+
+	p := tea.NewProgram(model{
+		sub:     make(chan struct{}),
+		spinner: spinner.NewModel(),
+	})
+
+	if p.Start() != nil {
+		fmt.Println("could not start program")
+		os.Exit(1)
+	}
+}