在 Django CreateView 中，使用类方法生成要在 get_context_data() 和 form_valid() 中使用的数据

Question

I'm actually working on a student project which i try to create a roguelike game on web using Python Django.

I'm actully confusing by my issue, to explain what i need to do is generate random characteristics in a character creation impacted by a choosen character class .

I want to send this characteristics to the user before he start the game. And use the characteristics I send him in my form_valid() to save the character in db.

I know that I a can use get_context_data() to send some information to my template but I don't know if can use the data send by get_context_data() to the template in form_valid().

Actually I'm succed with the a CreateView to save a character with random characteristics by a choosen character class, see the code bellow.

models.py

class CharacterClass(models.Model):
    name = models.CharField(max_length=20,
                            blank=True,
                            null=True)
    minHpMax = models.PositiveIntegerField(default=10,
                                           validators=[MinValueValidator(10)],
                                           blank=False,
                                           null=False)
    minStrength = models.IntegerField(default=1,
                                      validators=[MinValueValidator(0)],
                                      blank=False,
                                      null=False)
    minAgility = models.IntegerField(default=1,
                                     validators=[MinValueValidator(0)],
                                     blank=False,
                                     null=False)
    minInt = models.IntegerField(default=1,
                                 validators=[MinValueValidator(0)],
                                 blank=False,
                                 null=False)
    minPhysResis = models.IntegerField(default=0,
                                       validators=[MinValueValidator(0)],
                                       blank=False,
                                       null=False)
    minMagRes = models.IntegerField(default=0,
                                    validators=[MinValueValidator(0)],
                                    blank=False,
                                    null=False)

    def __str__(self):
        return f'{self.id}: {self.name}'

    def generateHpMax(self):
        return random.randint(self.minHpMax, self.minHpMax + 10)

    def generateStrength(self):
        return random.randint(self.minStrength, self.minStrength + 10)

    def generateAgility(self):
        return random.randint(self.minAgility, self.minAgility + 10)

    def generateIntelligence(self):
        return random.randint(self.minInt, self.minInt + 10)

    def generatePR(self):
        return random.randint(self.minPhysResis, self.minPhysResis + 10)

    def generateMR(self):
        return random.randint(self.minMagRes, self.minMagRes + 10)


class Character(models.Model):
    name = models.CharField(max_length=20,
                            default='Jon Doe',
                            blank=False,
                            null=False)
    characterClass = models.ForeignKey(CharacterClass,
                                       on_delete=models.CASCADE,
                                       related_name='characterClass')
    level = models.PositiveIntegerField(default=1,
                                        validators=[MinValueValidator(1)],
                                        blank=False,
                                        null=False)
    hpMax = models.PositiveIntegerField(default=10,
                                        validators=[MinValueValidator(0)],
                                        blank=False,
                                        null=False)
    hp = models.PositiveIntegerField(default=10,
                                     validators=[MinValueValidator(0)],
                                     blank=False,
                                     null=False)
    strength = models.IntegerField(default=1,
                                   validators=[MinValueValidator(0)],
                                   blank=False,
                                   null=False)
    agility = models.IntegerField(default=1,
                                  validators=[MinValueValidator(0)],
                                  blank=False,
                                  null=False)
    intelligence = models.IntegerField(default=1,
                                       validators=[MinValueValidator(0)],
                                       blank=False,
                                       null=False)
    physicalResistance = models.IntegerField(default=0,
                                             validators=[
                                                 MinValueValidator(0)],
                                             blank=False,
                                             null=False)
    magicalResistance = models.IntegerField(default=0,
                                            validators=[
                                                MinValueValidator(0)],
                                            blank=False,
                                            null=False)
    inventory = models.OneToOneField('Inventory',
                                     on_delete=models.PROTECT)

    def __str__(self):
        return f'{self.id}: {self.name} ' \
               f'[Lvl: {self.level}' \
               f'|Class: {self.characterClass}' \
               f'|HpM: {self.hpMax}' \
               f'|hp: {self.hp}' \
               f'|Str: {self.strength}' \
               f'|Ag: {self.agility}' \
               f'|Int: {self.intelligence}' \
               f'|Pr: {self.physicalResistance}' \
               f'|Mr: {self.magicalResistance}]'

    def get_absolute_url(self):
        return reverse('characterDetail', kwargs={'pk': self.pk})

views.py

    class GenerateCharacterView(CreateView):
    model = Character
    form_class = CharacterForm
    template_name = 'characterForm.html'

    def form_valid(self, form):
        # Creation of Character without db saving
        self.object = form.save(commit=False)

        # creation of empty inventory unique for the Character
        inventory = Inventory()
        inventory.save()
        self.object.inventory = inventory

        pkCharacterClass= form['characterClass'].value()
        currentCharacterClass = get_object_or_404(CharacterClass,
                                                  pk=pkCharacterClass)

        # for a CharacterClass found, get random characteristics for the Character in creation
        generatedHpMax = currentCharacterClass.generateHpMax()
        self.object.hpMax = generatedHpMax
        self.object.hp = generatedHpMax

        generatedStrength = currentCharacterClass.generateStrength()
        self.object.strength = generatedStrength

        generatedAgility = currentCharacterClass.generateAgility()
        self.object.agility = generatedAgility

        generatedIntelligence = currentCharacterClass.generateIntelligence()
        self.object.intelligence = generatedIntelligence

        generatedPhysicalResistance = currentCharacterClass.generatePR()
        self.object.physicalResistance = generatedPhysicalResistance

        generatedMagicalResistance = currentCharacterClass.generateMR()
        self.object.magicalResistance = generatedMagicalResistance

        # Enregistrement en BDD de l'objet et appel du super form valid pour
        # renvoie de la succes url défini en Model
        self.object.save()
        return super().form_valid(form)

forms.py

    class CharacterForm(forms.ModelForm):
    class Meta:
        model = Character
        # exclude = []
        fields = ['name', 'characterClass']

    name = forms.CharField(max_length=20, widget=widgets.TextInput(
        attrs={'placeholder': 'Enter Your Name'}
    ))

urls.py

    urlpatterns = [
    path('admin/', admin.site.urls),
    path('', IndexView.as_view(), name='home'),
    path('generateCharacter',
         GenerateCharacterView.as_view(),
         name='generateCharacter'),
    path('characterDetail/<int:pk>', CharacterDetailView.as_view(),
         name='characterDetail'),
]

Did you already succeed this kind of use ? Did you know if it's working ? and how ? Did you had some tips or advices for me ? I'm working on it form 2 days now and i'm going crazy.

---

Hello sorry for the this ticket, I may a mistake in what I show in it.

For now i use the code that I show in ticket for overpass my issue.

At this moment i can generate a character with random characteristics by choising a CharacterClass and a character name.

But what i want to do is generate the random characteristics when I come in the form page.

So i try to put on a page a button who call a path 'createCharacter/1' where '1' is the pk of my character class.

And i tried to generate the radom characteristics at this moment to show to the user the characteristics before the submit of the form.

And in the form only asked the character name.

So this was the code that I used previously

urls.py

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', IndexView.as_view(), name='home'),
    path('createCharacter/<int:characterClass>',
         CreateCharacterView.as_view(),
         name='createCharacter'),
    path('characterDetail/<int:pk>', CharacterDetailView.as_view(),
         name='characterDetail'),
]

views.py

class CreateCharacterView(CreateView):
    model = Character
    form_class = CharacterForm
    template_name = 'characterForm.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        classCharacter = get_object_or_404(CharacterClass ,self.kwargs['characterClass'])
        context['randomCarac'] = classCharacter.getRadomCarac()
        return context 

    def form_valid(self, form):
        self.object = form.save(commit=False)


        inventory = Inventory()
        inventory.save()
        self.object.inventory = inventory


        self.object.characterClass= context['characterClass']
        self.object.hpMax = context['hpMax ']
        self.object.hp = context['hpMax ']
        self.object.strength = context['strength ']
        self.object.agility = context['agility ']
        self.object.intelligence = context['intelligence  ']
        self.object.physicalResistance = context['physicalResistance ']
        self.object.magicalResistance = context['magicalResistance ']

        self.object.save()
        return super().form_valid(form)

models.py

class CharacterClass(models.Model):
    name = models.CharField(max_length=20,
                            blank=True,
                            null=True)
    minHpMax = models.PositiveIntegerField(default=10,
                                           validators=[MinValueValidator(10)],
                                           blank=False,
                                           null=False)
    minStrength = models.IntegerField(default=1,
                                      validators=[MinValueValidator(0)],
                                      blank=False,
                                      null=False)
    minAgility = models.IntegerField(default=1,
                                     validators=[MinValueValidator(0)],
                                     blank=False,
                                     null=False)
    minInt = models.IntegerField(default=1,
                                 validators=[MinValueValidator(0)],
                                 blank=False,
                                 null=False)
    minPhysResis = models.IntegerField(default=0,
                                       validators=[MinValueValidator(0)],
                                       blank=False,
                                       null=False)
    minMagRes = models.IntegerField(default=0,
                                    validators=[MinValueValidator(0)],
                                    blank=False,
                                    null=False)

    def __str__(self):
        return f'{self.id}: {self.name}'

    def generateHpMax(self):
        return random.randint(self.minHpMax, self.minHpMax + 10)

    def generateStrength(self):
        return random.randint(self.minStrength, self.minStrength + 10)

    def generateAgility(self):
        return random.randint(self.minAgility, self.minAgility + 10)

    def generateIntelligence(self):
        return random.randint(self.minInt, self.minInt + 10)

    def generatePR(self):
        return random.randint(self.minPhysResis, self.minPhysResis + 10)

    def generateMR(self):
        return random.randint(self.minMagRes, self.minMagRes + 10)

    def getRadomCarac(self):
        return {'hpMax': self.generateHpMax(),
                'strength': self.generateStrength(),
                'agility': self.generateAgility(),
                'intelligence': self.generateIntelligence(),
                'physicalResistance': self.generatePR(),
                'magicalResistance': self.getRadomCarac()}

---

That doesn't work. It seems i don't have acces to my context['something'] in the form_validation()

So i also tried to

class CreateCharacterView(CreateView):
    model = Character
    form_class = CharacterForm
    template_name = 'characterForm.html'
    classCharacter = get_object_or_404(CharacterClass ,self.kwargs['characterClass'])
    randomCarac = classCharacter.getRadomCarac()

def form_valid(self, form):
        # Do things here with randomCarac['something']

to have the value 'global' in the View to use when i want, the get_object_or_404() don't work

Answer 1

Ok guys this is the final code who work in my project

url.py

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', IndexView.as_view(), name='home'),
    path('generateCharacterByPk/<int:pk>', GenerateCharacterView2.as_view(),
         name='generateCharacterByPk'),
    path('generateCharacter', GenerateCharacterView.as_view(),
         name='generateCharacter'),
    path('characterDetail/<int:pk>', CharacterDetailView.as_view(),
         name='characterDetail'),
]

forms.py

class CharacterForm2(forms.ModelForm):
    class Meta:
        model = Character
        # exclude = []
        fields = ['name']

    name = forms.CharField(max_length=20, widget=widgets.TextInput(
        attrs={'placeholder': 'Enter Your Name'}
    ))

views.py

class GenerateCharacterView2(CreateView):
    model = Character
    form_class = CharacterForm2
    template_name = 'characterForm.html'

    def get_context_data(self, **kwargs):
        result = super().get_context_data(**kwargs)
        result['title'] = 'Create Character'
        return result

    def get(self, *args, **kwargs):
        currentCharacterClass = get_object_or_404(CharacterClass,
                                                  pk=self.kwargs['pk'])

        self.request.session['characterClass'] = self.kwargs['pk']
        self.request.session['HpMax'] = currentCharacterClass.generateHpMax()
        self.request.session['Strength'] = currentCharacterClass.generateStrength()
        self.request.session['Agility'] = currentCharacterClass.generateAgility()
        self.request.session['Intelligence'] = currentCharacterClass.generateIntelligence()
        self.request.session['PhysicalResistance'] = currentCharacterClass.generatePR()
        self.request.session['MagicalResistance'] = currentCharacterClass.generateMR()
        return super().get(self)

    def form_valid(self, form):
        # Création de l'objet sans enregistrement en base
        self.object = form.save(commit=False)

        # Création d'un inventaire vide unique au personnage avec affectation et récupéraction de la classe du personnage
        currentCharacterClass = get_object_or_404(CharacterClass,
                                                  pk=self.request.session['characterClass'])
        inventory = Inventory()
        inventory.save()

        # Constitution du personnage
        self.object.inventory = inventory
        self.object.characterClass = currentCharacterClass
        self.object.hpMax = self.request.session['HpMax']
        self.object.hp = self.request.session['HpMax']
        self.object.strength = self.request.session['Strength']
        self.object.agility = self.request.session['Agility']
        self.object.intelligence = self.request.session['Intelligence']
        self.object.physicalResistance = self.request.session['PhysicalResistance']
        self.object.magicalResistance = self.request.session['MagicalResistance']

        # Création en BDD du personnage
        self.object.save()
        return super().form_valid(form)

characterForm.html

{% extends 'base.html' %}

{% block page-top %}


    <form method="POST">
        {% csrf_token %}
        {% for field in form %}
            <div class="h5 font-weight-bold text-primary text-uppercase mb-1">
                <label>
                    {{ field.label }}:
                </label>
                <nav>
                    {{ field }}
                </nav>
            </div>
        {% endfor %}

        {{ request.session.characterClass }}
        {{ request.session.HpMax }}
        {{ request.session.Strength }}
        {{ request.session.Intelligence }}
        {{ request.session.Agility }}
        {{ request.session.PhysicalResistance }}
        {{ request.session.MagicalResistance }}
        <button type="submit">Valider</button>
    </form>


{% endblock %}

Thx @dirkgroten for your help, it was realy helpfull

Answer 2

If you want to create a random character when the form is shown to the user and keep that random character to save when the user submits the form (the name of the character), you'll need to persist the random character somehow.

You have a couple of options:

1. Create and save the character already when rendering the form the first time with the GET request (with a blank name) and include the id of the character in the form as hidden field so that when you submit the form you update the character with the name. You'll want to check that submitted id belongs to a "draft" character somehow in order to be sure the user doesn't steal another already existing character, so you might need to add a status field to your Character model. You would not use the CreateView here but a function-based view would be more appropriate.

2. You create the values for the character in the get() method of your view and store them in the request.session (see here ) so that you can retrieve said values from the session in the form_valid() method. This method seems easier to me. You can still use the CreateView here. You can display them in your template either directly using {{ request.session.<somekey> }} or by adding them to your context in get_context_data() in a format that might be easier to render in your template.

Submitting the random values via hidden form input fields is not an option, because anyone can always tamper the values submitted.

Note that I don't understand why your Character model doesn't have a reference to the User ( ForeignKey or OneToOneField ). It's not clear how you can check that the character belongs to this user and avoid a user stealing someone else's character. If you add this, then in option 1 you don't even need to check for an id since request.user can only have one "draft" Character .

Answer 3

May miss something in your solution, I've tried the solution 2, and i write the code bellow

index.html

    <button>
        <a href="{% url 'generateCharacterByPk' 1 %}">Play2(pk=1)</a>
    </button>

    <button>
        <a href="{% url 'generateCharacterByPk' 2 %}">Play2(pk=2)</a>
    </button>

urls.py

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', IndexView.as_view(), name='home'),
    path('generateCharacterByPk/<int:pk>',
         GenerateCharacterView2.as_view(),
         name='generateCharacterByPk'),
    path('generateCharacter',
         GenerateCharacterView.as_view(),
         name='generateCharacter'),
    path('characterDetail/<int:pk>', CharacterDetailView.as_view(),
         name='characterDetail'),
]

forms.py

class CharacterForm2(forms.ModelForm):
    class Meta:
        model = Character
        # exclude = []
        fields = ['name']

    name = forms.CharField(max_length=20, widget=widgets.TextInput(
        attrs={'placeholder': 'Enter Your Name'}
    ))

views.py

class GenerateCharacterView2(CreateView):
    model = Character
    form_class = CharacterForm2
    template_name = 'characterForm.html'

    def get_context_data(self, **kwargs):
        result = super().get_context_data(**kwargs)
        result['title'] = 'Create Character'
        return result

    def get(self, request, *args, **kwargs):
        request.session.characterClass = self.kwargs['pk']
        currentCharacterClass = get_object_or_404(CharacterClass,
                                                  pk=self.kwargs['pk'])
        request.session.characterClass = currentCharacterClass
        request.session.HpMax = currentCharacterClass.generateHpMax()
        request.session.Strength = currentCharacterClass.generateStrength()
        request.session.Agility = currentCharacterClass.generateAgility()
        request.session.Intelligence = currentCharacterClass.generateIntelligence()
        request.session.PhysicalResistance = currentCharacterClass.generatePR()
        request.session.MagicalResistance = currentCharacterClass.generateMR()
        return render(request, 'characterForm.html')

    def form_valid(self, form):
        # Création de l'objet sans enregistrement en base
        self.object = form.save(commit=False)

        # Création d'un inventaire vide unique au personnage avec affectation
        inventory = Inventory()
        inventory.save()

        self.object.inventory = inventory
        self.object.hpMax = request.session.characterClass
        self.object.hpMax = request.session.HpMax
        self.object.hp = request.session.HpMax
        self.object.strength = request.session.Strength
        self.object.agility = request.session.Agility
        self.object.intelligence = request.session.Intelligence
        self.object.physicalResistance = request.session.PhysicalResistance
        self.object.magicalResistance = request.session.MagicalResistance

        self.object.save()
        return super().form_valid(form)

characterForm.html

{% extends 'base.html' %}

{% block page-top %}


    <form method="POST">
        {% csrf_token %}
        {% for field in form %}
            <div class="h5 font-weight-bold text-primary text-uppercase mb-1">
                <label>
                    {{ field.label }}:
                </label>
                <nav>
                    {{ field }}
                </nav>
            </div>
        {% endfor %}

        {{ request.session.characterClass }}
        {{ request.session.HpMax }}
        {{ request.session.Strength }}
        {{ request.session.Intelligence }}
        {{ request.session.Agility }}
        {{ request.session.PhysicalResistance }}
        {{ request.session.MagicalResistance }}
        <button type="submit">Valider</button>
    </form>


{% endblock %}

And I have a weird reaction when I access to generateCharacterByPk/1 or generateCharacterByPk/2

First I see the random features randomly generated by my get on my page with a submit button.

When I click on the reload page and I end up with my form and a submit button but I don't see the features on my page anymore.

And when I validate the form, I get the following error:

AttributeError at /generateCharacterByPk/1
module 'django.http.request' has no attribute 'session'.
Request Method: POST
Request URL: http://127.0.0.1:8000/generateCharacterByPk/1
Django Version: 3.0.2
Exception Type: AttributeError
Exception Value:    
module 'django.http.request' has no attribute 'session'.
Exception Location: C:\Users\u049298\Desktop\PYTHON_DJANGO\projetWebRPG\app\views.py in form_valid, line 130
```