Flask-WTF FileField does not set data attribute to an instance of Werkzeug FileStorage

Question

Flask-WTF's documentation states that:

Flask-WTF provides you a FileField to handle file uploading, it will automatically draw data from flask.request.files if the form is posted. The data attribute of FileField will be an instance of Werkzeug FileStorage.

但是,当我使用时FileField,data发布后的属性不是FileStorage对象.相反,它是None(如果我enctype="multipart/form-data"按照文档中的建议定义我的表单)或文件名作为字符串(如果我没有定义enctype).

这是相关的Jinja2模板:

{% from "_form.html" import render_field %}
{% block body %}
  <section class="page-width-container" id="offset-content">
    <div id="utility-box">
      <h1 class="utility-header">Settings</h1>
      {{ message }}
      <form action="/settings" method="post" enctype="multipart/form-data">
        {{ render_field(form.photo) }}
        <input type="submit" class="form-action" value="Save" />
      </form>
    </div>
  </section>
{% endblock %}

_form.html宏:

{% macro render_field(field) %}
  <div class="field">
    {{ field.label }}
    <span class="form-input">{{ field()|safe }}</span>
    <div class="clear"></div>
    {% if field.errors %}
    <ul class="errors">
      {% for error in field.errors %}
      <li>{{ error }}</li>
      {% endfor %}
    </ul>
    {% endif %}
  </div>
{% endmacro %}

这是Python:

from flask import Blueprint, render_template, request
from flask.ext.wtf import Form
from flask.ext.wtf.file import FileField, FileRequired

settings_bp = Blueprint('settings', __name__)

class SettingsForm(Form):
  photo = FileField('Photo', validators=[
    FileRequired('no file!'),
  ])

@settings_bp.route('/settings', methods=['GET', 'POST'])
def login():
  form = SettingsForm(request.form)
  form.validate_on_submit()
  print(type(form.photo.data))
  return render_template('settings.html', form=form, message=form.photo.data)

使用元素enctype上的属性form,打印类型是NoneType; 没有enctype属性,打印类型是unicode.FileStorage文档中公布的对象也不是.

Answer 1

我查看了源代码(form.py)并找出了问题:FileStorage如果使用特定的表单初始化表单,则不会激活用对象替换默认数据属性的代码formdata.将formdata必须被保留未指定的文件功能的工作.替换此行:

form = SettingsForm(request.form)

有了这条线:

form = SettingsForm()

解决了这个问题.