What is the technique for submitting an error form again?

Question

Using Flask + Flask-Classy + WTForms, I try to implement a route, so when the user has an error in their input form, the application will again submit this form to the user, complete with what the user has already filled out. Thus, the user did not have to worry about re-entering all input forms: (s) he can fix the errors.

This is the code from my UserView class (FlaskView), which is a class of checkboxes class:

def post(self): form = forms.UserForm(request.form) if form.validate(): if form.id.data=='': user = models.Users() form.populate_obj(user) user.id = None db.session.add(user) else: user = models.Users.query.get(form.id.data) form.populate_obj(user) db.session.commit() return redirect(url_for('UserView:index')) else: return redirect(url_for('UserView:validation_error', error_form=form)) def validation_error(self, error_form): return render_template('users/form.html', form=error_form) 

You can see that in this attempt I am trying to create another method: validation_error , with an argument - what in my expectation - should contain all the form data. But it turns out I have a Jinja2 exception, UndefinedError: 'unicode object' has no attribute 'hidden_tag' . When I checked it, after validation_error , this form object changed somewhat from UserForm to some unicode object.

Any suggestion? Or am I trying to solve this problem in the wrong direction?

EDIT 1: more on how to display an error

As @Rawrgulmuffins added an answer on how to display an inline error (which I think is best, as the page will not get jumpy), here I pasted the code into my layout.html , which lists all the errors. It may not be as good as displaying a built-in error, but I think this is the easiest way. First I do an if for the form object, as this code also exists for all pages (I might have reorganized it even more)

  {% if form %} {% for error in form.errors %} <div class="alert alert-error"> <a class="close" data-dismiss="alert">×</a> <strong>{{ form[error].label }} {{form.errors[error][0] }}</strong> </div> {% endfor %} {% endif %} 

Screenshot:

Answer 1

I am adding my answer to extend the swdev answer for those who do not understand why it can just display the template and show errors.

Each field in the form contains an error attribute, which will be filled after verification (after form.validate() ). These errors will be contained in the form object. So you can say something like

 {% if field.errors %} <span class="error help-inline">{{ field.errors|join(', ') }}</span> {% endif %} 

sample source file . It is very elegant because you can just say

  return render_template('users/form.html', form=form) 

and if he gets the first render form without errors and displays errors only in the second rendering of the form.

I'm not sure why Swdev tried to redirect the form, causing it to be manipulated right now. I am looking through the Werkzeug code right now to find out if I can find the answer.

Answer 2

Oh, how stupid I am. Immediately after I rested a bit, I found a simple answer, that is, instead of switching to another presentation method:

 else: return redirect(url_for('UserView:validation_error', error_form=form)) 

I can easily display the template:

  return render_template('users/form.html', form=form) 

It's simple;)