{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 绑定属性\n",
    "\n",
    "NiceGUI 能够直接将 UI 元素绑定到模型。可以对 UI 元素的 `text`、`value` 或 `visibility` 属性以及（嵌套的）类属性进行绑定。每个元素都提供了如 `bind_value` 和 `bind_visibility` 之类的方法来创建与相应属性的双向绑定。要定义单向绑定，请使用这些方法的 `_from` 和 `_to` 变体。只需将这些方法的参数设置为模型的属性即可创建绑定。值将在立即更新，并在其中一个值更改时更新。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from nicegui import ui\n",
    "\n",
    "class Demo:\n",
    "    def __init__(self):\n",
    "        self.number = 1\n",
    "\n",
    "demo = Demo()\n",
    "v = ui.checkbox('visible', value=True)\n",
    "with ui.column().bind_visibility_from(v, 'value'):\n",
    "    ui.slider(min=1, max=3).bind_value(demo, 'number')\n",
    "    ui.toggle({1: 'A', 2: 'B', 3: 'C'}).bind_value(demo, 'number')\n",
    "    ui.number().bind_value(demo, 'number')\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 绑定到字典\n",
    "\n",
    "在这里，我们将标签的文本绑定到一个字典。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "<nicegui.elements.button.Button at 0x26e32a9e1d0>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from nicegui import ui\n",
    "\n",
    "data = {'name': 'Bob', 'age': 17}\n",
    "\n",
    "ui.label().bind_text_from(data, 'name', backward=lambda n: f'Name: {n}')\n",
    "ui.label().bind_text_from(data, 'age', backward=lambda a: f'Age: {a}')\n",
    "\n",
    "ui.button('Turn 18', on_click=lambda: data.update(age=18))\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 绑定到变量\n",
    "\n",
    "在这里，我们将 `datepicker` 的值绑定到普通变量。因此，我们使用了包含所有全局变量的字典 `globals()`。这个示例基于[官方的 `datepicker` 示例](https://nicegui.io/documentation/date#input_element_with_date_picker)。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "from nicegui import ui\n",
    "\n",
    "date = '2023-01-01'\n",
    "\n",
    "with ui.input('Date').bind_value(globals(), 'date') as date_input:\n",
    "    with ui.menu() as menu:\n",
    "        ui.date(on_change=lambda: ui.notify(f'Date: {date}')).bind_value(date_input)\n",
    "    with date_input.add_slot('append'):\n",
    "        ui.icon('edit_calendar').on('click', menu.open).classes('cursor-pointer')\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 绑定到存储\n",
    "\n",
    "绑定也可以与 `app.storage` 一起使用。在这里，我们在访问之间存储 `textarea` 的值。同一个用户的所有标签页之间也会共享这个笔记。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "from nicegui import app, ui\n",
    "\n",
    "@ui.page('/')\n",
    "def index():\n",
    "    ui.textarea('This note is kept between visits').classes('w-full').bind_value(app.storage.user, 'note')\n",
    "\n",
    "# ui.run()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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