form.is_valid() always returning false

Model class

class Fuzz_Engine(models.Model):
    id = PositiveTinyIntField(primary_key = True)
    engine_name = models.CharField(max_length=16)
    version = mo开发者_JAVA百科dels.CharField(max_length = 16)

    class Meta:
        db_table = 'fuzz_engine'
        unique_together = ('engine_name', 'version')

class AddFuzzEngineForm(ModelForm):
    class Meta:
        model = Fuzz_Engine

View Class

def addengine(request)
    if request.method == 'POST':
        form = AddFuzzEngineForm(request.POST)

        # input validation for add phone model form
        if form.is_valid():
            fuzzEngineToAdd = Fuzz_Engine (engine_name = request.POST['engine_name'], version = request.POST['version'])
            fuzzEngineToAdd.save(force_insert=True)

            return render_to_response('fuzz/fuzz_cengine_results.html', {'fid': fuzzEngineToAdd.id,'fe': fuzzEngineToAdd,},context_instance=RequestContext(request))
    else:
        form = AddFuzzEngineForm()

    return render_to_response('fuzz/add_fuzz_engine.html', {'form': form},context_instance=RequestContext(request))

I have looked into a few similar questions on this issue, tried to print out the errors but doesn't seem to appear.

Django Formsets - form.is_valid() is False preventing formset validation form.is_valid() always returning false

I have a feeling that the cause of the error lies in the structure of my model form class.

The .is_valid is false as I have placed a code in that if statement and it doesn't run, however if I have an else statement(which is not here) for if it is not valid, it will appear.

Can anyone provide another way of debugging this kind of error?

Couple of issues, it's hard to debug the code if the code you paste in isn't formatted well. The indentations were a mess so I'm not sure if that's causing a problem.

It seems like you are manually assigning a foreign key for your model. I would suggest just letting django handle the id for the model:

class Fuzz_Engine(models.Model):
    engine_name = models.CharField(max_length=16)
    version = models.CharField(max_length = 16)

    class Meta:
        db_table = 'fuzz_engine'
        unique_together = ('engine_name', 'version')

Your form looks fine:

class AddFuzzEngineForm(ModelForm):
    class Meta:
        model = Fuzz_Engine

Some problems I see in your views include:

1. you shouldn't use request.POST['field_names'] directly. you should be getting the cleaned_data from your form.

2. you can save the form directly because it is a ModelForm. if you need the instance that you just created, that is what is returned from the save method, you can set a variable and use that as shown below.

   def addengine(request)
       if request.method == 'POST':
           form = AddFuzzEngineForm(request.POST)
   
           if form.is_valid():
               instance = form.save()
               return render_to_response('fuzz/fuzz_cengine_results.html', {'fid': instance.id,'fe': instance,},context_instance=RequestContext(request))
       else:
           form = AddFuzzEngineForm()
   
       return render_to_response('fuzz/add_fuzz_engine.html', {'form': form},context_instance=RequestContext(request))
   

3. With your original view, it looks like you are trying to save a Fuzz_Engine instance with no id.

DTing has some great points, but I suspect your actual problem is related to your explicit definition of the id field on your model. Unless you have a really good reason, you should never do this - Django defines an autoincrement field automatically, and there is rarely any point overriding this, unless you are using a legacy db that can't be changed.

In your case, you have defined it as a tinyint without autoincrement. That means that field is going to be required on any form, as it needs to be specified manually every time you create a new instance. You haven't shown the template you're using to display the form so it's impossible to be sure, but I imagine you're not showing this field at all.

If you really really want to carry on doing it this way, you will need to specify exclude = ('id',) on the form Meta. Then in your is_valid clause, taking on board DTing's recommendations, you'll need to do this:

if form.is_valid():
    instance = form.save(commit=False)
    instance.id = some_function_for_calculating_id()
    instance.save()

But as I say, you shouldn't be doing that at all.