django dynamic forms setting max_length property

Question

I am creating a 'Forms Management' system for my application.

I am creating a forms dynamically using a custom form 'factory' method.

Form data is in a json file.

I can create a forms.CharField and set the label, required, initial and help_text properties.

When I try to set the max_length property I do not get any error message, but the resulting HTML does not contain the max_length attribute.

In static (class) forms defined as

class SearchAccountForm(forms.Form):
    provider_code = forms.CharField(
        label='Provider:', 
        max_length=100, 
        required=True, 
        widget=forms.TextInput(attrs={'class': 'form-control'}))

The resulting HTML contains the max_length attribute.

<label for="id_provider_code">Provider:</label>
</th><td><input type="text" name="provider_code" class="form-control" maxlength="100" required id="id_provider_code">

So what's up with max_length??

Json file

{
    "form1": [
        {
            "fld_name": "customer_name",
            "fld_type": "CharField",
            "fld_label": "Cust Name",
            "fld_required": "False",
            "fld_maxLength": 5,
            "initial": "Dr John"
        },
        {
            "fld_name": "customer_number",
            "fld_type": "CharField",
            "fld_label": "Cust #",
            "fld_required": "True",
            "fld_maxLength": 15,
            "help_text": "Enter account number"
        },
        {
            "fld_name": "customer_type",
            "fld_type": "CharField",
            "fld_label": "Customer Type",
            "fld_required": "False"
        }
    ]
}

and the forms.py factory method

from django import forms
import json

def dynfrm():
    f = open('blog/frmJson/frm1.json')

    data = json.load(f)
    fields = {}
    for i in data['form1']:     ## form1 = form name in json file
        print(i)
        ## add to fields list
        if i['fld_type'] == 'CharField':
            fields[i["fld_name"]] = forms.CharField()
            if 'fld_label' in i:
                fields[i["fld_name"]].label = i["fld_label"]
            if 'fld_required' in i:
                if i["fld_required"] == 'False':
                    fields[i["fld_name"]].required = False
                else:
                    fields[i["fld_name"]].required = True
            if 'initial' in i: fields[i["fld_name"]].initial = i["initial"]
            if 'help_text' in i: fields[i["fld_name"]].help_text = i["help_text"]
## next line not working
            if 'fld_maxLength' in i: fields[i["fld_name"]].max_length = i["fld_maxLength"]

            fields[i["fld_name"]].widget = forms.TextInput()

    return type('DynForm',  # form name is irrelevant
                (forms.BaseForm,),
                {'base_fields': fields})    

my view

def vdynfrm(request):
    if request.method == 'POST':
        form = dynfrm(request.POST)
        if form.is_valid():
            pass
            ## all good
    else:
        form = dynfrm()

    ##return render(request, "blog/dfrm.html",{'form': form})
    return render(request, "blog/searchAccount.html",{'form': form})

and the resulting HTML

<div class="form-group">
   <form action="/searchAccount/" method="post">
      <table>
         <tr>
            <th><label for="id_customer_name">Cust Name:</label></th>
            <td><input type="text" name="customer_name" value="Dr John" id="id_customer_name">/td> 
         </tr>
         <tr>
            <th><label for="id_customer_number">Cust #:</label></th>
            <td><input type="text" name="customer_number" required id="id_customer_number"><br> 
                <span class="helptext">Enter account number</span></td>
            </tr>
            <tr>
               <th><label for="id_customer_type">Customer Type:</label></th>
               <td><input type="text" name="customer_type" id="id_customer_type"></td>
            </tr>    
      </table>
         
      <input type="submit" value="Submit">
   </form>
</div>

Answer 1

The max_length property only works when you send the context correctly to your template file.

your forms.py

class SearchAccountForm(forms.Form):
    provider_code = forms.CharField(
        label='Provider:',
        max_length=100,
        required=True,
        widget=forms.TextInput(attrs={'class': 'form-control'}))

With function based view:

def home(request):
    if request.method == 'POST':
        form = SearchAccountForm(request.POST)
        if form.is_valid():
            provider_c= form.cleaned_data['provider_code']
            print('Provider Code :',provider_c)
            return HttpResponseRedirect('/thanks/')
    else:
        form = SearchAccountForm()

    return render(request, 'home/index.html', {'form': form})

def thanks(req):
    return render(req, 'home/thanks.html')

If you forget to give else condition for get request method, so you will not receive django's inbuild error messages as well as max_length etc.

With Class based view it can be handled easily:

from django.views.generic.edit import FormView

class Home(FormView):
    template_name = 'home/index.html'
    form_class = SearchAccountForm
    success_url = '/thanks/'

    def form_valid(self, form):
        print(form)
        print('Provider Code : ', form.cleaned_data['provider_code'])
        return super().form_valid(form)

def thanks(req):
    return render(req, 'home/thanks.html')

From both the examples above max_length property is working properly because its get request got handled.

Check your views.py, it may help.