ndb多对多，检索关系之一的列表 [英] ndb many to many, retrieve list of one of the relation

问题描述

我有这张表

  class ClubMembership（GCModel）：
 member = ndb.KeyProperty（kind = 'User'，required = True）
 club = ndb.KeyProperty（kind ='Club'，required = True）
 is_active = ndb.BooleanProperty（default = True）
 membership_type = ndb。 StringProperty（options = set（[MEMBER，TRAINER，OWNER]），default =MEMBER，
 required = True）
  

然后在表俱乐部我这里

<$ p俱乐部（GCModel）：
@property
def成员（自我）：
返回ClubMembership.query（ndb.AND（ClubMembership.club == self.key，
ClubMembership.membership_type ==会员，
ClubMembership.is_active == True））

我真正需要的是检索 User 的列表。我应该怎么做？

获取这个查询，比使用for循环获取每个成员使用它的关键字？

我试着用 ndb.get_multi 来使用成员但它不起作用。
这样的东西

  members = ClubMembership.query（ndb.AND（ClubMembership.club == self.key， 
 ClubMembership.membership_type ==MEMBER，
 ClubMembership.is_active == True），projection = ['member']）。fetch（）
 ndb.get_multi（members）
  




解决方案

get_multi 在键列表上工作，您有一个ClubMembership实例的列表。您需要为每个人获取成员键：

  memberships = ClubMembership.query（...）
 member_keys = [会员中m为m.member] 
 members = ndb.get_multi（member_keys）
  

I've this table

class ClubMembership(GCModel):
    member = ndb.KeyProperty(kind='User', required=True)
    club = ndb.KeyProperty(kind='Club', required=True)
    is_active = ndb.BooleanProperty(default=True)
    membership_type = ndb.StringProperty(choices=set(["MEMBER", "TRAINER", "OWNER"]), default="MEMBER",
                                     required=True)

Then in the Table Club i've this

class Club(GCModel):
    @property
    def members(self):
        return ClubMembership.query(ndb.AND(ClubMembership.club == self.key,
                                            ClubMembership.membership_type == "MEMBER",
                                            ClubMembership.is_active == True))

what i actually need is to retrive the list of User. how should i do?

fetch this query, than have a for loop that fetches each member using its key?

i tried to use ndb.get_multi using the projection on member but it does not work. something like this

members= ClubMembership.query(ndb.AND(ClubMembership.club == self.key,
                                            ClubMembership.membership_type == "MEMBER",
                                            ClubMembership.is_active == True),projection=['member']).fetch()
ndb.get_multi(members)

解决方案

get_multi works on a list of keys, you have a list of ClubMembership instances. You need to get the member key for each one:

memberships = ClubMembership.query(...)
member_keys = [m.member for m in memberships]
members = ndb.get_multi(member_keys)

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