如何在不覆盖当前记录的情况下预填充和保存 Django 模型记录？答案

【问题标题】：How can I prefill and save a Django Model record without overwriting the current one?如何在不覆盖当前记录的情况下预填充和保存 Django 模型记录？
【发布时间】：2020-10-29 22:53:18
【问题描述】：

我有一个表单，我想预先填写用户之前的输入。我使用Form(instance = object) 代码来做到这一点。但是，在用户提交表单后，之前的表单条目会被新的表单条目更新。我不希望这样，而是希望它创建一个不同的实例以跟踪更改历史记录。有什么方法可以让我在预先填写表格的同时做到这一点？

view.py

from django.shortcuts import render, redirect
from .models import Topic, Entry
from .forms import TopicForm, EntryForm

def edit_entry(request, entry_id):
    entry = Entry.objects.get(id = entry_id)
    topic = entry.topic

    if request.method != 'POST':
        # Initial request; pre-fill for with the current entry.
        form = EntryForm(instance = entry)

    else:
        # POST data submitted.
        form = EntryForm(instance = entry, data = request.POST)
        if form.is_valid():
            form.save()
            return redirect('learning_logs:topic', topic_id = topic.id)

    context = {'entry': entry, 'topic': topic, 'form': form}
    return render(request, 'learning_logs/edit_entry.html', context)

forms.py

from django import forms
from .models import Topic, Entry

class TopicForm(forms.ModelForm):
    class Meta:
        model = Topic
        fields = ['text']
        labels = {'text':''}

class EntryForm(forms.ModelForm):
    class Meta:
        model = Entry
        fields = ['text']
        labels = {'text':''}
        widgets = {'text': forms.Textarea(attrs = {'cols': 80, 'spellcheck':True})}

models.py

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

class Topic(models.Model):  
    text = models.CharField(max_length = 200)
    date_added = models.DateTimeField(auto_now_add = True)
    owner = models.ForeignKey(User, on_delete = models.CASCADE)

class Entry(models.Model):
    topic = models.ForeignKey(Topic, on_delete = models.CASCADE)
    text = models.TextField()
    date_added = models.DateTimeField(auto_now_add = True)

【问题讨论】：

标签： python-3.x django-models

【解决方案1】：

您可以将条目的主键.pk设置为None，这样它就会创建一条新记录：

from django.shortcuts import render, redirect
from .models import Topic, Entry
from .forms import TopicForm, EntryForm

def edit_entry(request, entry_id):
    entry = Entry.objects.get(id = entry_id)
    topic = entry.topic

    if request.method != 'POST':
        # Initial request; pre-fill for with the current entry.
        form = EntryForm(instance=entry)

    else:
        # POST data submitted.
        entry.pk = None  # &leftarrow; set .pk entry to None
        form = EntryForm(request.POST, instance=entry)
        if form.is_valid():
            form.save()
            return redirect('learning_logs:topic', topic_id = topic.id)

    context = {'entry': entry, 'topic': topic, 'form': form}
    return render(request, 'learning_logs/edit_entry.html', context)

【讨论】：