WTForms render_field() method reference for-loop variables

Question

I'm using Flask to create a web app. I'm trying to create a form using Flask-WTForms by iterating through a list passed in the render_template() method. However, I can't reference the variable in the for-loop inside the template.

View

class FormExample(Form):
    category1 = StringField("Category 1")
    category2 = StringField("Category 2")

categories = ['category1', 'category2']
def form():
    form = FormExample(request.form)
    return_template("form.html", categories=categories, form=form)

_formhelpers.html (suggested to use under the docs)

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

Template (form.html)

<form method="POST">
  {% for category in categories %}
    {{render_field(form.category)}}
  {% endfor %}
</form>

When trying to reference form.category in form.html I'm given the following error through the Flask debugger:

jinja2.exceptions.UndefinedError: '__main__.EvaluateCaseForm object' has no attribute 'category'

I've already looked at the official documentation here and couldn't find the answer. I've also tried referencing {{render_field({{ form.category }})}}, {{render_field(form.{{category}})}}, and {{render_field({% form.category %})}}

Is there a way to reference the for-loop variable category inside the render_field() method?

Why not {% for field in form %}{{ render_field(field) }}{% endfor %}? Are you trying to handle categories not matching the fields in your form? — snakecharmerb
– snakecharmerb, Commented Aug 4, 2018 at 5:01
@snakecharmerb the issue I'm having is that form.category is being read as though the variable form has an attribute called category. However, I want the value for category to be the value based on the for-loop. Does that make sense? — Max
– Max, Commented Aug 6, 2018 at 20:47

snakecharmerb · Accepted Answer · 2018-08-07 03:43:39Z

1

WTForms uses the __getitem__ protocol to allow fields can be accessed like dictionary values, for example form[fieldname].

So in your code, replace form.category with form[category]:

<form method="POST">
  {% for category in categories %}
    {{ render_field(form[category]) }}
  {% endfor %}
</form>

answered Aug 7, 2018 at 3:43

snakecharmerb

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Comments

clime · Accepted Answer · 2018-08-03 23:33:50Z

0

Is there a way to reference the for-loop variable category inside the render_field() method?

Yup:

   {% for category in categories %}
     {{render_field(category)}}
   {% endfor %}

answered Aug 3, 2018 at 23:33

clime

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1 Comment

Max Over a year ago

I apologize I don't think I made myself clear. I need to access the form attributes form.category1 and form.category2. I just updated the question with a bit more information to hopefully make it more clear. Trying to pass in (category) just passes in a string and not a form attribute.

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