在 Django 中无法 post 数据到外键 table

Question

我绝对是 Django 的初学者，我正在尝试通过将值填充到 POST 来检查方法外键 table。我有两个 table。请指导我哪里错了。

Table for Category that has 2 entries, i.e., Coffee(PK = 1) and Desserts (PK = 2)

Table for Items

来自models.py:

class Category(models.Model):
    cId = models.AutoField(primary_key=True)
    categoryName = models.CharField(max_length=20, unique=True)

    def __str__(self):
        return self.categoryName
        # return[self.categoryName, self.cId]
        # return self.cId
    
class Item(models.Model):
    Id = models.AutoField(primary_key=True)
    itemName  = models.CharField(max_length=30,unique=True)
    cId = models.ForeignKey(Category,on_delete=CASCADE)

来自 views.py: def main（请求）： return 渲染（请求，“index.html”）

def send(request):
    if request.method == "POST":
        a = request.POST.get("a");
        b = request.POST.get("b");
        obj = Item(itemName = a, cId =b);
        obj.save()
        
        return HttpResponse("sent")
    else:
        return HttpResponse("form submission failed")

来自 urls.py(app):

urlpatterns = [
    path('', views.main, name="main"),
    path('send', views.send, name='send')
   
]

来自HTML:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    {% load static %}

    <link rel="stylesheet" href="{% static 'css.css' %}">

    <title>CHECK-POST-METHOD</title>
</head>

<body>
    <div class = "container">
        <form method = "post" action = "send" class = "form">
            {% csrf_token %}
            <label for="a">Item Name</label>
            <input type="text" name="a" id="a" maxlength="30">
            <label for="b">PASS FOREIGN KEY--CATEGORY ID</label>
            <input type="number" name="b" id="b" maxlength="5">
            <button type="submit">SUBMIT</button>

        </form>

    </div>

    <script src="{% static 'js.js' %}"></script>
  
</body>

</html>

我无法使用以下条目填充项目 table：

我无法解决以下错误：

Answer 1

cId 需要一个 Category 对象，但你给了它 '1'。如果您想为名为 foo 的 ForeignKey 指定主键，您可以使用 <i>foo</i>_id，所以在这种情况下 cId_id:

def send(request):
    if request.method == 'POST':
        a = request.POST.get('a')
        b = request.POST.get('b')
        obj = Item(itemName=a, <strong>cId_id=b</strong>)
        obj.save()
        
        return HttpResponse("sent")
    else:
        return HttpResponse("form submission failed")

Answer 2

如错误中所示，Cid 必须是类别的实例所以您的视图如下所示：

def send(request):
    if request.method == "POST":
        a = request.POST.get("a");
        b = request.POST.get("b");
        c_id = Category.objects.get(pk=b)
        obj = Item(itemName=a, cId=b);
        obj.save()

        return HttpResponse("sent")
    else:
        return HttpResponse("form submission failed")

Answer 3

由于cId需要是Category类型的对象，可以使用Django的get_object_or_404函数。如果 HTML 发布的 cId 无效，则此函数会自动引发 404 响应。

from django.shortcuts import get_object_or_404

def send(request):
    if request.method == "POST":
        a = request.POST.get("a");
        b = request.POST.get("b");
        b_obj = get_object_or_404(Category, b)
        obj = Item(itemName = a, cId =b_obj)
        obj.save()
        
        return HttpResponse("sent")
    else:
        return HttpResponse("form submission failed")

在 Django 中无法 post 数据到外键 table

Unable to post data to foreign key table in Django

python

mysql

django

foreign-keys