Django Form If条件在view.py中有2个实例 [英] Django Form If condition in view.py with 2 instance

问题描述

要保存在Django中以表格形式输入的数据，我试图使它像这样
，我将其放入模型中。py

TO SAVE DATA that is inputted in form in Django i tried tomake it like this I put this in my model.py

class Item(models.Model):
    CATEGORY = (
        ('Gudang Kering', 'Gudang Kering'),
        ('Gudang Basah','Gudang Basah'),
        )
    name = models.CharField(max_length=200,null= True)
    stock = models.IntegerField(default='0', blank=False, null=True)
    category = models.CharField(max_length=200,null= True,choices=CATEGORY)
    reorderlevel = models.IntegerField(default='0', blank=False, null=True)
    maxreorderlevel = models.IntegerField(default='0', blank=False, null=True)
    description = models.CharField(max_length=200,null= True, blank= True)
    date_created = models.DateTimeField(auto_now_add= True)
    tags = models.ManyToManyField(Tag)
    
    def __str__(self):
        return self.name

class Issue(models.Model):
    STATUS = (
        ('Pending', 'Pending'),
        ('Granted','Granted'),
        ('Denied','Denied'),
        )
    customer = models.ForeignKey(Customer, null=True, on_delete= models.SET_NULL)
    item = models.ForeignKey(Item, null=True, on_delete= models.SET_NULL)
    quantity = models.IntegerField(default='0', blank=False, null=True)
    date_created = models.DateTimeField(auto_now_add=True, auto_now=False)
    status = models.CharField(max_length=200,null= True, choices=STATUS)

然后在view.py中定义这样的形式

Then in view.py i define the form like this

def updateIssue(request, pk):
    issue = Issue.objects.get(id=pk)
    item = Item.objects.all()
    form = UpdateIssueForm(instance=issue)
    if request.method == 'POST':
        form = UpdateIssueForm(request.POST,instance=issue)
        #print ('printing:',request.POST)
        if form.is_valid():
            instance = form.save(commit=False)
            if instance.status == 'Granted':
                item.stock -= instance.quantity
                instance.save()
                item.save()
            else:
        instance.save()

        return redirect('/')
    

    context = {'form':form}
    return render(request,'accounts/issue_form.html',context)``

目标

如果instance == Granted
，item.stock将减少instance.quantity
的数量并将被保存。

else

实例将被保存而不会影响第二个模型的库存

The Goal
if instance == "Granted"
the item.stock will be decreased on the amount of instance.quantity and will be saved.
else
instance will just be saved without affecting the stock from the 2nd model

错误

    item = Item.objects.all()

即使调用item.stock也具有0属性，即使我在该表的数据库中有输入数据

even when called the item.stock have 0 attribute even when i have input data in database for that table

推荐答案

无需获取 Item ，因为我们可以访问 Item 使用问题对象（例如 issue.item ）与问题相关。这只是来自 docs 的示例：

There is no need to get Item since we can access the Item related to Issue using the Issue object like issue.item. This is just an example from docs:

文章模型具有一个字段报告者，该报告者是实现为Reporter模型的ForeignKey。

Article model has a field reporter which is a ForeignKey realted to Reporter model. Using Article object the Reporter object is accessed.

>>> new_article = r.article_set.create(headline="John's second story", pub_date=date(2005, 7, 29))
>>> new_article
<Article: John's second story>
>>> new_article.reporter
<Reporter: John Smith>
>>> new_article.reporter.id
1

因此，我们可以访问 Item 使用问题

Like so, we can access the Item using Issue

def updateIssue(request, pk):
    issue = Issue.objects.get(id=pk)  # we have our Issue here
    form = UpdateIssueForm(instance=issue)
    if request.method == 'POST':
        form = UpdateIssueForm(request.POST,instance=issue)

        if form.is_valid():
            instance = form.save(commit=False)
            if instance.status == 'Granted':
                issue.item.stock -= instance.quantity   # access Item by using Issue object's related field with name item
                issue.item.save() # save the Item first
                instance.save() # then the Issue
            else: 
                instance.save()

        return redirect('/')
    

    context = {'form':form}
    return render(request,'accounts/issue_form.html',context)

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