测试 Django ModelForm 是否有实例 [英] Test if Django ModelForm has instance

问题描述

如果我进入编辑表单，我想显示一条警告消息，如果我进入 Django ModelForm 的创建表单，我想隐藏它.

I would like to display a warning message if I am into an editing form and hide it if I am in a creation form of a Django ModelForm.

form.is_bound 告诉我之前是否填充了表单，但如何测试 ModelForm 是否使用现有实例设置?

form.is_bound tell me if the form was previously populated but how to test if the ModelForm was set with an existing instance ?

我试过这个 hasattr(form.instance, 'pk') 但这是正确的方法吗?

I tried this hasattr(form.instance, 'pk') but is it the right way to do so ?

干杯，

纳蒂姆

推荐答案

尝试检查 form.instance.pk 是否为 None.

Try checking if form.instance.pk is None.

hasattr(form.instance, 'pk') 将始终返回 True，因为每个模型实例都有一个 pk 字段，即使它尚未保存到数据库中.

hasattr(form.instance, 'pk') will always return True, because every model instance has a pk field, even when it has not yet been saved to the database.

正如@Paullo 在评论中指出的那样，如果您手动定义主键并指定默认值，则这将不起作用，例如default=uuid.uuid4.

As pointed out by @Paullo in the comments, this will not work if you manually define your primary key and specify a default, e.g. default=uuid.uuid4.

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