将属性动态附加到 ndb.Model 的实例并将它们放在 to_dict() 表示中
•浏览 1
Dynamically attach properties to an instance of ndb.Model and have them in the to_dict() representation
我正在通过 Google App Engine NDB 编写一个 REST api
我排除了现有库，因为我需要控制事务和缓存。
出于类似的原因，我排除了 Google Endpoints，也因为我不想使用他们提供的 javascript 客户端。
在评估架构决策时，我遇到了一些问题和奇怪的情况，这是因为我对 python 和 pythonic 风格的经验可能不够丰富。
在这一刻，我试图提出一些应该塑造我的代码库的指导方针：
- 在 Handlers -> 创建对象的字典表示
并将它们作为 json 返回；执行身份验证和授权
支票
- 将ndb交互封装在Services中
- 模型类总是接收模型对象或键作为参数并返回模型对象或模型列表
- 模型类被导入并在服务中使用
我遇到的一件特别的事情是
我使用映射模型实现了多对多关系，例如
UserOrganizationMembership，具有 User 和 Organization
的密钥
现在，在我的服务中，有时我想返回一个对象，其中包含当前用户所属的组织列表，并递归地获取每个组织中的公司：
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):我这样做
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):在突出显示的行中，我将动态属性 \\'companies\\' 附加到组织模型
现在，如果我在处理程序中调用此方法，当我创建字典表示以输出 json 时，ndb.Model.to_dict() 实现会忽略动态附加的属性。
我尝试过的一个解决方案是(在我的处理程序中)
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):但我不喜欢它，因为我需要知道每个组织都有一个\\'companies\\'属性，而且代码看起来有点复杂而且不明显
另一种方法是覆盖 ndb.Model.to_dict()
隔离动态附加属性并提供字典表示，这简化了我在处理程序中的代码，让我只对服务返回的内容调用 to_dict()。
从 google.appengine.ext 导入 ndb
导入实用程序
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):您对这种方法有什么建议吗？任何想法将不胜感激！
ndb 通过 Expando 类型支持动态属性。
而不是将模型定义为：
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):使用 Expando:
定义它
'organizations': [
{
'name': 'TEST'
'companies': [ {company1}, {company2}]
},
{
...
}
]
def user_organizatios_with_companies(user):
def fetch_companies(x):
x.companies = Company.by_organization(x) #NOTICE THIS
return x
user_organizations = [ membership.organization.get() for membership in UserOrganizationMembership.by_user(user)]
return [fetch_companies(x) for x in user_organizations]
xs = Service.user_organizatios_with_companies(u)
organizations = [x.to_dict() for x in xs]
for x in xrange(0,len(xs)):
organizations[x]['companies'] = xs[x].to_dict()
class BaseModel(ndb.Model):
created = ndb.DateTimeProperty(auto_now_add = True)
updated = ndb.DateTimeProperty(auto_now = True)
# App Engine clock times are always
# expressed in coordinated universal time (UTC).s
def to_dict(self, include=None, exclude=None):
result = super(BaseModel,self).to_dict(include=include, exclude=exclude)
result['key'] = self.key.id() #get the key as a string
# add properties dynamically added to the class
dynamic_vars = {k:v for (k,v) in vars(self).iteritems() if not k.startswith('_')}
for prop, val in dynamic_vars.iteritems():
result[prop] = val.to_dict() if not isinstance(val, list) else [x.to_dict() for x in val]
return util.model_db_to_object(result)
class BaseModel(ndb.Model):
class BaseModel(ndb.Expando):现在，如果你写 x.companies = [...]，调用 _to_dict() 将输出那些公司。当你put()这些实体时要小心，因为任何动态添加的属性也会被放入数据存储中。