CODEWITHSUNDEEP
pythongoogle-app-enginegoogle-cloud-datastore
userBG
userBG

Reputation: 7180

App Engine appending items to ListProperty

I think I'm loosing my mind, why doens't the following work?

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()

I get this error:

BadValueError: Property childrenKeys is required

The doc says:

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.

So the way I see it, I'm getting the default (an empty list) and appending a new value to it and the saving it.

Upvotes: 5

Views: 2964

Answers (2)

systempuntoout
systempuntoout

Reputation: 74134

You should remove the p.childrenKeys assignment:

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

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

Upvotes: 8

Dan Sanderson
Dan Sanderson

Reputation: 2111

Replace this:

p.childrenKeys = p.childrenKeys.append('newchildkey')

with this:

p.childrenKeys.append('newchildkey')

append() returns None, which can't be assigned to p.childrenKeys.

Upvotes: 5

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