如何在成功的POST请求后更改Class-Based-Views的表单字段填充？

huangapple
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英文:

How can I change form field population *after* successful POST request for Class-Based-Views

问题

  1. # forms.py
  2. class CalculatorForm(forms.Form):
  3.     body_weight = forms.FloatField(required=False)
  5.     def clean(self):
  6.         cleaned_data = super().clean()
  7.         if cleaned_data['body_weight'] is None:
  8.             cleaned_data['body_weight'] = 50.0
  9.         return cleaned_data
  1. # views.py
  2. class CalculatorView(FormView):
  3.     template_name = 'myapp/mycalculator.html'
  4.     form_class = CalculatorForm
  6.     def get_context_data(self, res=None, **kwargs):
  7.         context = super().get_context_data(**kwargs)
  8.         if res is not None:
  9.             context['result'] = res
  10.         return context
  12.     def form_valid(self, form, *args, **kwargs):
  13.         res = form.cleaned_data['body_weight'] / 2
  14.         return render(
  15.             self.request,
  16.             self.template_name,
  17.             context=self.get_context_data(res=res, **kwargs)
  18.         )
英文:

I want to change the forms initial field population. Here is the catch: I want to change it for the POST request and not for the GET request.

Let's say my app offers a calculation based on a body weight input. If the user inputs a body weight calculation happens with that weight, if not a default of 50 is used. So it is allowed to let the field empty. But after the calculation ran, I want to display that the value used for calculation was 50. That's why I want to populate the field with 50 after the form was initially submitted with an empty value.

  1. # forms.py
  2. class CalculatorForm(forms.Form):
  3.     body_weight = forms.FloatField(required=False)
  5.     def clean(self):
  6.         cleaned_data = super().clean()
  7.         if cleaned_data['body_weight'] is None:
  8.             cleaned_data['body_weight'] = 50.0
  9.         # ideally I want to put the logic here
  10.         # self.data[bpka] = 50.0 --> AttributeError: This QueryDict instance is immutable
  11.         # self.fields['body_weight'] = 50.0 --> does not work
  12.         # self.initial.update({'body_weight': 50.0}) --> does not work
  13.         return cleaned_data

I feel like the problem is that I can not reach the bound fields from the clean() method.

If it is not possible within the form the logic has to go to the view I guess. Feel free to modify here:

  1. class CalculatorView(FormView):
  2.     template_name = 'myapp/mycalculator.html'
  3.     form_class = CalculatorForm
  5.     def get_context_data(self, res=None, **kwargs):
  6.         context = super().get_context_data(**kwargs)
  7.         if res is not None:
  8.             context['result'] = res
  9.         return context
  11.     def form_valid(self, form, *args, **kwargs):
  12.         # form['body_weight'] = 50.0 --> does not work
  13.         res = form.cleaned_data['body_weight'] / 2
  14.         return render(
  15.             self.request,
  16.             self.template_name,
  17.             context=self.get_context_data(res=res, **kwargs)
  18.         )

答案1

得分: 1

你可以重写 .form_valid 方法，因为该方法在提交有效的表单数据时被调用。通过这种方式，创建一个带有所需 initial 值的新实例 CalculatorForm，而不是返回默认的 HttpResponseRedirect，而是使用新表单渲染页面。

保留你的表单的 clean 方法不变，然后将修改后的 form.cleaned_data 作为新实例化表单的初始字典传递。

forms.py

  1. class CalculatorForm(forms.Form):
  2.     body_weight = forms.FloatField(required=False)
  4.     def clean(self):
  5.         cleaned_data = super().clean()
  6.         if cleaned_data['body_weight'] is None:
  7.             cleaned_data['body_weight'] = 50.0
  8.         return cleaned_data

views.py

  1. class CalculatorView(FormView):
  2.     template_name = "myapp/mycalculator.html"
  3.     form_class = CalculatorForm
  5.     def get_context_data(self, res=None, **kwargs):
  6.         context = super().get_context_data(**kwargs)
  7.         if res is not None:
  8.             context['result'] = res
  9.         return context
  10.     
  11.     def form_valid(self, form):
  12.         body_weight = form.cleaned_data["body_weight"]
  14.         res = body_weight / 2
  16.         form = self.form_class(initial=form.cleaned_data)
  17.         return render(
  18.             self.request, 
  19.             self.template_name, 
  20.             context=self.get_context_data(res=res, form=form, **kwargs)
  21.         )

myapp/mycalculator.html

  1. <body>
  2.     <form action="{% url 'calculator' %}" method="post">
  3.         {% csrf_token %}
  4.         {{ form }}
  5.         <button type="submit">Send</button>
  6.     </form>
  7.     {% if result %}
  8.         <p>{{ result }}</p>
  9.     {% endif %}
  10. </body>
英文:

You can override .form_valid since the method is called when valid form data has been POSTed. In this way creating a new instance of CalculatorForm with the desired initial value and instead of returning a HttpResponseRedirect which is default render the page with the new form.

Keep the clean method of your form as is and then pass the modified form.cleaned_data as the initial dict for your newly instantiated form.

forms.py

  1. class CalculatorForm(forms.Form):
  2.     body_weight = forms.FloatField(required=False)
  4.     def clean(self):
  5.         cleaned_data = super().clean()
  6.         if cleaned_data[&#39;body_weight&#39;] is None:
  7.             cleaned_data[&#39;body_weight&#39;] = 50.0
  8.         return cleaned_data

views.py

  1. class CalculatorView(FormView):
  2.     template_name = &quot;myapp/mycalculator.html&quot;
  3.     form_class = CalculatorForm
  5.     def get_context_data(self, res=None, **kwargs):
  6.         context = super().get_context_data(**kwargs)
  7.         if res is not None:
  8.             context[&#39;result&#39;] = res
  9.         return context
  10.     
  11.     def form_valid(self, form):
  12.         body_weight = form.cleaned_data[&quot;body_weight&quot;]
  14.         res = body_weight / 2
  16.         form = self.form_class(initial=form.cleaned_data)
  17.         return render(
  18.             self.request, 
  19.             self.template_name, 
  20.             context=self.get_context_data(res=res, form=form, **kwargs)
  21.         )

myapp/mycalculator.html

  1. &lt;body&gt;
  2.     &lt;form action=&quot;{% url  &#39;calculator&#39; %}&quot; method=&quot;post&quot;&gt;
  3.         {% csrf_token %}
  4.         {{ form }}
  5.         &lt;button type=&quot;submit&quot;&gt;Send&lt;/button&gt;
  6.     &lt;/form&gt;
  7.     {% if result %}
  8.         &lt;p&gt;{{ result }}&lt;/p&gt;
  9.     {% endif %}
  10. &lt;/body&gt;

huangapple
  • 本文由 发表于 2023年6月29日 22:12:58
  • 转载请务必保留本文链接：https://go.coder-hub.com/76581885.html
  • django
  • django-forms
  • django-views
  • python
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