Django自动设置表单提交用户为模型外键字段的报错与实现需求

Hey there! Let's fix that save() missing required positional argument 'self' error while automatically assigning the current user to your model's foreign key field. I'll walk you through a solid, working example step by step—no fancy tricks, just straightforward Django practices.

Let's start with a simple model that has a user foreign key (linked to Django's built-in User model) and some other fields. This is our base:

# models.py
from django.db import models
from django.contrib.auth.models import User

class Post(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    title = models.CharField(max_length=200)
    content = models.TextField()

    def __str__(self):
        return self.title

We don't want the user to manually select their own account, so we'll exclude the user field from our form. Django will handle setting it automatically:

# forms.py
from django import forms
from .models import Post

class PostForm(forms.ModelForm):
    class Meta:
        model = Post
        fields = ['title', 'content']  # Only include fields users need to fill out

I'll show you two common, error-free ways to assign the user. Pick whichever fits your workflow better.

Approach 1: Set the User Directly in the View (Most Straightforward) #

This method uses commit=False to create a model instance without saving it to the database first. We can then add the user before saving:

# views.py
from django.shortcuts import render, redirect
from .forms import PostForm
from django.contrib.auth.decorators import login_required

@login_required  # Make sure only logged-in users can submit the form
def create_post(request):
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            # Create the Post instance but don't save to DB yet
            post = form.save(commit=False)
            # Assign the current logged-in user
            post.user = request.user
            # Now save the complete instance to the database
            post.save()
            return redirect('post_list')  # Replace with your desired redirect URL
    else:
        form = PostForm()
    return render(request, 'create_post.html', {'form': form})

Approach 2: Override the Form's Save Method #

If you prefer to keep view logic clean, you can move the user assignment into the form itself by overriding the save() method:

First, update your form:

# forms.py (updated)
from django import forms
from .models import Post

class PostForm(forms.ModelForm):
    class Meta:
        model = Post
        fields = ['title', 'content']

    # Override save to accept a user parameter
    def save(self, user, commit=True):
        # Get the unsaved instance from the parent save method
        instance = super().save(commit=False)
        # Assign the user
        instance.user = user
        # Save to DB if commit is True
        if commit:
            instance.save()
        return instance

Then update your view to pass the user to the form's save method:

# views.py (updated for Approach 2)
from django.shortcuts import render, redirect
from .forms import PostForm
from django.contrib.auth.decorators import login_required

@login_required
def create_post(request):
    if request.method == 'POST':
        form = PostForm(request.POST)
        if form.is_valid():
            # Pass the current user to our custom save method
            form.save(user=request.user)
            return redirect('post_list')
    else:
        form = PostForm()
    return render(request, 'create_post.html', {'form': form})

Chances are you tried calling the save method directly on the model class instead of an instance. For example:

# ❌ Wrong! This will throw the error because save() is an instance method
if form.is_valid():
    Post.save(user=request.user)

You need to create an instance first (like we did with form.save(commit=False)) before calling save().

Here's a quick template to render the form (save this as create_post.html):

<form method="POST">
    {% csrf_token %}
    {{ form.as_p }}
    <button type="submit">Submit Post</button>
</form>

内容的提问来源于stack exchange，提问作者Derrick Sherrill