调用save（）后Django模型没有被保存？

Question

我重写了一个ModelForm的保存方法。我解析一个Excel文件，如果有一些值，我更新窗体的实例相关对象中的数量。它是第一次，当实例没有相关的对象。但是第二次，当我更新这些值时，没有任何反应。我不确定它是否与commit参数有关。

编辑 - 相关代码：

def save(self, commit=True): 
    """ 
    Overrides the save method in order to add the product inventory items listed in 
    the uploaded Excel file, if one was uploaded. 
    """ 
    inventory = super(AddOrChangeProductsInventoryForm, self).save(commit) 

    self._update_inventory_items_quantities() 

    if not commit: 
     inventory.save() 
     self.save_m2m() 

    return inventory 

def _update_inventory_items_quantities(self): 
    inventory = self.instance 

    if len(self.excel_data_dict) == 0: 
     return inventory 

    non_existing_products = [] 

    for i, product_sku in enumerate(self.excel_data_dict['SKU']): 
     quantity = self.excel_data_dict['Cantidad'][i] 
     new_item = inventory.productinventoryitem_set.filter(product__sku=product_sku).first() 

     if new_item is None: 
      product = Product.objects.filter(sku=product_sku).first() 

      if product is None: 
       # TODO: Raise warning in view 
       non_existing_products.append(product_sku) 
       continue 

      new_item = ProductInventoryItem() 
      new_item.product = product 
      new_item.inventory = inventory 

     new_item.quantity += quantity 
     # TODO: Check why after first update it's not being updated 

Answer 1

如果模型有任何许多一对多的关系，那么你需要确保在组合使用self.save_m2m()与保存方法。下面是一个简单的例子：

# save method of your forms.ModelForm class. 
def save(self): 
    obj = super(MyModelForm, self).save(commit=False) 
    obj.save() 
    self.save_m2m() 
    return obj 

Answer 2

当commit为False时，您正在保存表单。 替换（第10行）：

if not commit: 

与：

if commit: 

UPDATE：

new_item是inventory.productinventoryitem_set.filter(product__sku=product_sku).first()

或

ProductInventoryItem() 

新副本

这是本地变量，它不更新inventory。执行该功能后，所有这些更改都将被破坏。您需要将更改存储在inventory中。

for obj in self.instance.productinventoryitem_set.all(): 
    obj.quantity += 2 
    obj.save() 

然后你保存更改前销毁：

当你在重写_save_m2m。

你可以做这样的事情：

def save(self, commit=True): 

    inventory = super(AddOrChangeProductsInventoryForm, self).save(commit) 

    self._update_inventory_items_quantities(inventory, commit) 

    return inventory 

def _update_inventory_items_quantities(self, inventory, commit): 

    if len(self.excel_data_dict) == 0: 
     return inventory 

    non_existing_products = [] 

    for i, product_sku in enumerate(self.excel_data_dict['SKU']): 
     quantity = self.excel_data_dict['Cantidad'][i] 
     new_item = inventory.productinventoryitem_set.filter(product__sku=product_sku).first() 

     if new_item is None: 
      product = Product.objects.filter(sku=product_sku).first() 

      if product is None: 
       # TODO: Raise warning in view 
       non_existing_products.append(product_sku) 
       continue 

      new_item = ProductInventoryItem() 
      new_item.product = product 
      new_item.inventory = inventory 

     new_item.quantity += quantity 
     if commit: 
      new_item.save()