jinja2.exceptions.UndefinedError: 'render_field' is undefined

Question

所以我刚开始将 Wtforms 与 Flask 结合使用，我设置了基本 class 并在 forms.py 中定义了我的所有字段，如您在此处所见...

from wtforms import Form, TextField, validators, PasswordField, DateField

class AddAccount(Form):
    username = TextField('Username', [validators.Length('min=3, max=20')])
    email = TextField('Email', [validators.Length('min=1, max=255')])
    karma = TextField('Karma', [validators.Length('min=1, max=10000000')])
    password = PasswordField('Password', [validators.Length('min=6, max=255')])

然后我将 AddAccount class 导入到 views.py 中，如您所见...

from forms import AddAccount

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

    form = AddAccount(request.form)

    if request.method == 'POST' and form.validate():
        print('POST request')


    return render_template('add_account.html', form=form)

这是模板文件...

{% extends 'layout.html' %}

{% block body %}
    <br>
    <div class="jumbotron text-center">
       <h1>Add an Account</h1>
       <hr>
       <form action="{{url_for('add_account')}}">
            <div class="form-group">
                {{render_field(form.username, class_='form-control')}}
            </div>
            <div class="form-group">
                {{render_field(form.email, class_='form-control')}}    
            </div>
            <div class="form-group">
                {{render_field(form.password, class_='form-control')}}
            </div>
            <div class="form-group">
                {{render_field(form.karma, class_='form-control')}}
            </div>
        </form>
    </div>
{% endblock %}

整个装置导致此错误 jinja2.exceptions.UndefinedError: 'render_field' is undefined，我完全不知道为什么会发生或如何修复它。任何帮助将不胜感激。

如果有帮助...这是堆栈跟踪...

Traceback (most recent call last):
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1997, in __call__
    return self.wsgi_app(environ, start_response)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1985, in wsgi_app
    response = self.handle_exception(e)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1540, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\_compat.py", line 33, in reraise
    raise value
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1517, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\_compat.py", line 33, in reraise
    raise value
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1612, in full_dispatch_request
    rv = self.dispatch_request()
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\app.py", line 1598, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "E:\Python\manager\views.py", line 37, in add_account
    return render_template('add_account.html', form=form)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\templating.py", line 134, in render_template
    context, ctx.app)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\flask\templating.py", line 116, in _render
    rv = template.render(context)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\jinja2\asyncsupport.py", line 76, in render
    return original_render(self, *args, **kwargs)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\jinja2\environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\jinja2\environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Users\Hassan\AppData\Local\Programs\Python\Python36\lib\site-packages\jinja2\_compat.py", line 37, in reraise
    raise value.with_traceback(tb)
  File "E:\Python\manager\templates\add_account.html", line 1, in top-level template code
    {% extends 'layout.html' %}
  File "E:\Python\manager\templates\layout.html", line 22, in top-level template code
    {% block body %}{% endblock %}
  File "E:\Python\manager\templates\add_account.html", line 10, in block "body"
    {{render_field(form.username, class_='form-control')}}
jinja2.exceptions.UndefinedError: 'render_field' is undefined

Answer 1

您认为为什么会有 render_field 功能？关于这个的任何参考，你在读什么文档？无论如何，这应该可以解决问题：

{% extends 'layout.html' %}

{% block body %}
    <br>
    <div class="jumbotron text-center">
       <h1>Add an Account</h1>
       <hr>
       <form action="{{url_for('add_account')}}">
            <div class="form-group">
                {{form.username(class_='form-control')}}
            </div>
            <div class="form-group">
                {{form.email(class_='form-control')}}    
            </div>
            <div class="form-group">
                {{form.password(class_='form-control')}}
            </div>
            <div class="form-group">
                {{form.karma(class_='form-control')}}
            </div>
        </form>
    </div>
{% endblock %}

另见 Add a css class to a field in wtform。

Answer 2

您可以创建一个新文件 _formhelpers.html，内容为

{% macro render_field(field) %}
  <dt>{{ field.label }}
  <dd>{{ field(**kwargs)|safe }}
  {% if field.errors %}
    <ul class=errors>
    {% for error in field.errors %}
      <li>{{ error }}</li>
    {% endfor %}
    </ul>
  {% endif %}
  </dd>
{% endmacro %}

然后，在将表单加载到 VIEW 之前包含相同的内容

{% block body %}
<h1>Register </h1>
{% from '/includes/_formhelpers.html' import render_field %}
<form method="POST" action="">
    <div class="form-group">
        {{render_field(form.name ,class_="form-control")}}
    </div>
    <p><input type="submit" class="btn btn-primary" value="Submit"></p>
</form>

这应该可以解决您的问题。谢谢！

可以找到文档here

Answer 3

您需要创建部分文件，例如 _formhelpers.html。
转到 this link 并复制模板代码中的表单并将其粘贴到您创建的 _formhelpers.html 中
在您的模板文件中添加这行代码

{% from '_formhelpers.html' import render_field %}

Answer 4

您必须使用此代码：

{% from "includes/_formhelpers.html" import render_field %}

模板文件。

或者您可以包括 _fromhelpers.html。

jinja2.exceptions.UndefinedError: 'render_field' is undefined

jinja2.exceptions.UndefinedError: 'render_field' is undefined

python

jinja2

flask

wtforms