通过flask bootstrap将flask wtforms验证传递给引导警报

这里是新的flask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。该按钮基本上利用wtforms来验证只能上载csv和txt文件。上传工作正常,但如何将验证错误作为引导警报传递到屏幕?例如:

1. 按下“上传”按钮将生成“未选择文件”警报。
2. 用jpeg按upload将生成“错误的文件格式”

如有任何建议,我们将不胜感激!

我的表格。

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")

我的路由器

@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)

最后是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 %}