Create BookInstance form

本章節演示如何定義一個頁面/表單,以創建 BookInstance 物件。這很像我們用來創建書本 Book 物件的表單。


打開 /controllers/bookinstanceController.js,並在檔案最上方,加入以下幾行:

const { body,validationResult } = require('express-validator/check');
const { sanitizeBody } = require('express-validator/filter');

Controller—get route

At the top of the file, require the Book module (needed because each BookInstance is associated with a particular Book).

var Book = require('../models/book');

Find the exported bookinstance_create_get() controller method and replace it with the following code.

// Display BookInstance create form on GET.
exports.bookinstance_create_get = function(req, res, next) {

    .exec(function (err, books) {
      if (err) { return next(err); }
      // Successful, so render.
      res.render('bookinstance_form', {title: 'Create BookInstance', book_list:books});


The controller gets a list of all books (book_list) and passes it to the view bookinstance_form.pug (along with the title)

Controller—post route

Find the exported bookinstance_create_post() controller method and replace it with the following code.

// Handle BookInstance create on POST.
exports.bookinstance_create_post = [

    // Validate fields.
    body('book', 'Book must be specified').isLength({ min: 1 }).trim(),
    body('imprint', 'Imprint must be specified').isLength({ min: 1 }).trim(),
    body('due_back', 'Invalid date').optional({ checkFalsy: true }).isISO8601(),

    // Sanitize fields.

    // Process request after validation and sanitization.
    (req, res, next) => {

        // Extract the validation errors from a request.
        const errors = validationResult(req);

        // Create a BookInstance object with escaped and trimmed data.
        var bookinstance = new BookInstance(
          { book:,
            imprint: req.body.imprint,
            status: req.body.status,
            due_back: req.body.due_back

        if (!errors.isEmpty()) {
            // There are errors. Render form again with sanitized values and error messages.
                .exec(function (err, books) {
                    if (err) { return next(err); }
                    // Successful, so render.
                    res.render('bookinstance_form', { title: 'Create BookInstance', book_list : books, selected_book : , errors: errors.array(), bookinstance:bookinstance });
        else {
            // Data from form is valid.
   (err) {
                if (err) { return next(err); }
                   // Successful - redirect to new record.

The structure and behaviour of this code is the same as for creating our other objects. First we validate and sanitize the data. If the data is invalid, we then re-display the form along with the data that was originally entered by the user and a list of error messages. If the data is valid, we save the new BookInstance record and redirect the user to the detail page.


Create /views/bookinstance_form.pug and copy in the text below.

extends layout

block content

  form(method='POST' action='')
      label(for='book') Book:
      select#book.form-control(type='select' placeholder='Select book' name='book' required='true')
        for book in book_list
          if bookinstance
            option(value=book._id selected=( ? 'selected' : false)) #{book.title}
            option(value=book._id) #{book.title}

      label(for='imprint') Imprint:
      input#imprint.form-control(type='text' placeholder='Publisher and date information' name='imprint' required='true' value=(undefined===bookinstance ? '' : bookinstance.imprint))
      label(for='due_back') Date when book available:
      input#due_back.form-control(type='date' name='due_back' value=(undefined===bookinstance ? '' : bookinstance.due_back))

      label(for='status') Status:
      select#status.form-control(type='select' placeholder='Select status' name='status' required='true')
        option(value='Maintenance') Maintenance
        option(value='Available') Available
        option(value='Loaned') Loaned
        option(value='Reserved') Reserved

    button.btn.btn-primary(type='submit') Submit

  if errors
      for error in errors
        li!= error.msg

The view structure and behaviour is almost the same as for the book_form.pug template, so we won't go over it again.

備註: The above template hard-codes the Status values (Maintenance, Available, etc.) and does not "remember" the user's entered values. Should you so wish, consider reimplementing the list, passing in option data from the controller and setting the selected value when the form is re-displayed.

What does it look like?

Run the application and open your browser to http://localhost:3000/. Then select the Create new book instance (copy) link. If everything is set up correctly, your site should look something like the following screenshot. After you submit a valid BookInstance, it should be saved and you'll be taken to the detail page.

Next steps