通过 Flask-Bootstrap 将 Flask WTForms 验证传递给 Bootstrap 警报

Question

这里是 Flask 新用户...我正在为我的 Flask 应用程序构建一个漂亮的文件上传按钮。该按钮实质上使用 WTForms 来验证只能上传 csv 和 txt 文件。上传有效，但如何将验证错误作为 bootstrap 警报传递到屏幕？例如：

按下上传按钮将生成警报 "no file selected"
使用 jpeg 按下上传将生成 "wrong file format"

如有任何建议，我们将不胜感激！

我的forms.py:

class UploadForm(FlaskForm):
    validators = [FileRequired(message='There was no file!'),
                  FileAllowed(['csv', 'txt'], message='Must be a csv file!')]

    input_file = FileField('', validators=validators)
    submit = SubmitField(label="Upload")

我的route.py:

@app.route('/upload', methods=['GET', 'POST'])
def upload():

    form = UploadForm()

    if request.method == 'POST' and form.validate_on_submit():
        input_file = request.files['input_file']

        # Do stuff
        filename = secure_filename(input_file.filename)

        # save file to disk to some folder defined in a separate config file....
        data = os.path.join(SOME_UPLOAD_FOLDER, filename)
        input_file.save(data)

        return redirect(url_for('upload'))

else:
    return render_template('upload.html', form=form)

最后 HTML/CSS/JS:

{% extends "bootstrap/base.html" %}
{% import "bootstrap/wtf.html" as wtf %}

{% block html_attribs %} lang="en" charset="utf-8"{% endblock %}

{% block metas %}
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
{% endblock %}


{% block styles %}

    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"
          integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

    <style>
        #browsebutton {
            background-color: white;
        }

        #my-file-selector {
            display: none;
        }
    </style>


{% endblock %}

{% block content %}

    <div class="container">
        <div class="jumbotron">
            <h3>File Uploader Example</h3>


            <div class="row">
                <form class="form-inline center-block" action="/upload" method="POST" enctype="multipart/form-data">
                    {{ form.hidden_tag() }}
                    <div class="input-group">
                        <label id="browsebutton" class="btn btn-default input-group-addon" for="my-file-selector">
                            {{ form.input_file(id="my-file-selector") }}
                            Browse...
                        </label>
                        <input type="text" class="form-control" readonly>
                    </div>
                    {{ form.submit(class_="btn btn-primary") }}
                </form>
            </div>
        </div>
    </div>

{% endblock %}


{% block scripts %}

    <! -- jquery -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <!-- Latest compiled and minified JavaScript -->
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"
            integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>

    <!-- pretty upload button -->
    <script>
    $(function() {

      // We can attach the `fileselect` event to all file inputs on the page
      $(document).on('change', ':file', function() {
        var input = $(this),
            numFiles = input.get(0).files ? input.get(0).files.length : 1,
            label = input.val().replace(/\/g, '/').replace(/.*\//, '');
        input.trigger('fileselect', [numFiles, label]);
      });

      // We can watch for our custom `fileselect` event like this
      $(document).ready( function() {
          $(':file').on('fileselect', function(event, numFiles, label) {

              var input = $(this).parents('.input-group').find(':text'),
                  log = numFiles > 1 ? numFiles + ' files selected' : label;

              if( input.length ) {
                  input.val(log);
              } else {
                  if( log ) alert(log);
              }

          });
      });

    });
    </script>

{% endblock %}

Answer 1

如果您使用的是 WTForms，我建议您使用宏来呈现您的表单域。它很详细here, and you can get an example there（你可以在网上找到一些其他的帮助你定制而不是必须从头开始写）。

请注意，在 WTForm 的文档中，宏 render_field() 检查您的字段是否有错误：

{% if field.errors %}
  <ul class=errors>
  {% for error in field.errors %}
    <li>{{ error }}</li>
  {% endfor %}
  </ul>
{% endif %}

您当然可以决定不使用宏，在这种情况下，您可以直接在您的 html 表单中使用上面的代码片段 form.input_file.errors 而不是 field.errors

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