如何在Python Django中添加數組字段

Question

我正在製作電子商務網站，我想將Cart元素存儲在整數數組字段中。我使用PostGreSql作爲我的數據庫。 我已經通過擴展Django用戶模型創建了購物車模型。這裏是我的模型

class UserCart(models.Model): 
    user=models.OneToOneField(User,on_delete=models.CASCADE) 
    user_product=models.IntegerField(blank=True, null=True) 
    cart_products = ArrayField(
     models.IntegerField(blank=True), 
     default = list 
    ) 

User.profile = property(lambda u:UserCart.objects.get_or_create(user=u)[0]) 

下面是我的Form.py.我從Django的進口形式 從.models只創造了基本形式 從django.db進口車型導入UserCart 從django.contrib.postgres.fields導入ArrayField

class UserCartForm (forms.ModelForm): 

    class Meta: 
     model= UserCart 
     fields = ('user_product',) 

我已經搜索了很多互聯網上，但爲無法找到相關answer.I想，只要用戶點擊加入購物車按鈕時，得到的product_id存儲在cart_products array.I某處讀取ArrayFields表現爲在Django列表，所以這裏是我的views.py

@login_required 
def user_cart(request): 
    if request.method=='POST': 
     form=UserCartForm(request.POST , instance=request.user.profile) 
     if form.is_valid(): 
      post = form.save(commit=False) 
      post.cart_products.append(99) 
      post.save() 
      return HttpResponseRedirect('/user_login/loggedin') 
     else: 
      HttpResponse("Error") 
    else: 
     user=request.user 
     profile=user.profile 
     form= UserCartForm(instance=profile) 
     args={} 
     args.update(csrf(request)) 
     args['form']=form 
     return render_to_response('cartapi.html' ,args) 

它的給我的錯誤

AttributeError at /cart/ac/ 
'NoneType' object has no attribute 'append' 
Request Method: POST 
Request URL: http://localhost:8000/cart/ac/ 
Django Version: 1.11.2 
Exception Type: AttributeError 
Exception Value: 
'NoneType' object has no attribute 'append' 
Exception Location: C:\Users\Muhammad     
Jawad\AppData\Local\Programs\Python\Python36-32\mysite\cart\views.py in 
user_cart, line 19 
Python Executable: C:\Users\Muhammad 
Jawad\AppData\Local\Programs\Python\Python36-32\python.exe 

如果我救cart_products這樣

post.cart_products=99 

然後拋出這個錯誤

column "cart_products" is of type int4range but expression is of type integer 
LINE 1: ...er_id" = 1, "user_cart" = 3000, "cart_products" = 99 WHERE "... 
                 ^
HINT: You will need to rewrite or cast the expression. 
Request Method: POST 
Request URL: http://localhost:8000/cart/ac/ 
Django Version: 1.11.2 
Exception Type: ProgrammingError 
Exception Value: 
column "cart_products" is of type int4range but expression is of type integer 
LINE 1: ...er_id" = 1, "user_cart" = 3000, "cart_products" = 99 WHERE "... 
                 ^
HINT: You will need to rewrite or cast the expression. 

請幫我在這matter.Summarizing我的問題： 我如何獲得user_product作爲id並將其保存在cart_products中

Answer 1

點

變化侑意見這樣

views.py

@login_required 
def user_cart(request): 
    if request.method=='POST': 
     form=UserCartForm(request.POST , instance=request.user.profile) 
     if form.is_valid(): 
      post = form.save(commit=False) 
      if post.cart_products: 
       post.cart_products.append(99) 
      else: 
       post.cart_products = [99] 
      post.save() 
      return HttpResponseRedirect('/user_login/loggedin') 
     else: 
      HttpResponse("Error") 
    else: 
     user=request.user 
     profile=user.profile 
     form= UserCartForm(instance=profile) 
     args={} 
     args.update(csrf(request)) 
     args['form']=form 
     return render_to_response('cartapi.html' ,args) 

Answer 2

通過當前的代碼看起來沒什麼問題的，但由於某種原因，你的情況是cart_productsNone，所以你可以嘗試這樣

if post.cart_products: 
    post.cart_products.append(99) 
else: 
    post.cart_products = [99]