program.go

package main

import (
	"fmt"
	"os"

	tea "github.com/charmbracelet/bubbletea"
)

type PageNumber int

const (
	Page1View PageNumber = iota + 1
	Page2View
)

type SomeMessage struct{}

type model struct {
	page  PageNumber
	items []string
}

func (m model) Init() tea.Cmd {
	return nil
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.KeyMsg:
		if msg.Type == tea.KeyEnter && m.page == Page1View {
			return m, goToNextPage(&m)
		} else {
			return m, tea.Quit
		}
	}
	return m, nil
}

func (m model) View() string {
	view := ""

	if m.page == Page1View {
		view += fmt.Sprintf("page: %v\n", m.page)
		view += fmt.Sprintf("items: %v %v %v\n", m.items[0], m.items[1], m.items[2])
		view += "press enter to go to next page"
	} else if m.page == Page2View {
		view += fmt.Sprintf("page: %v\n", m.page)
		view += fmt.Sprintf("items: %v %v %v\n", m.items[0], m.items[1], m.items[2])
		view += "press enter to go to exit"
	}

	return view
}

func goToNextPage(m *model) tea.Cmd {
	return func() tea.Msg {
		m.items[0], m.items[1], m.items[2] = "four", "five", "six" // items get updated properly
		m.page = Page2View                                         // but page does NOT get updated
		return SomeMessage{}
	}
}

func main() {
	model := model{
		page:  Page1View,
		items: []string{"one", "two", "three"},
	}

	program := tea.NewProgram(model)

	if _, err := program.Run(); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}

> go run .

page: 1
items: one two three
press enter to go to next page

> Enter is pressed

page: 1
items: four five six
press enter to go to next page