python - App Engine 将项目附加到 ListProperty

Question

我想我疯了，为什么下面的方法不起作用？

class Parent(db.Model):
    childrenKeys = db.ListProperty(str,indexed=False,default=None)

p = Parent.get_or_insert(key_name='somekey')
p.childrenKeys = p.childrenKeys.append('newchildkey')
p.put()

我收到这个错误:

BadValueError: Property childrenKeys is required

文档说:

default is the default value for the list property. If None, the default is an empty list. A list property can define a custom validator to disallow the empty list.

所以在我看来，我正在获取默认值(一个空列表)并向其附加一个新值并保存它。

Answer 1

您应该删除 p.childrenKeys 分配:

class Parent(db.Model):
    childrenKeys = db.ListProperty(str,indexed=False,default=[])

p = Parent.get_or_insert('somekey')
p.childrenKeys.append('newchkey')
p.put()