无法从数据存储实体访问ID属性 [英] Unable to access ID property from a datastore entity
问题描述
使用Google App Engine SDK和Python,我遇到了一个问题:我无法访问给定实体属性的ID属性。我可以访问的唯一属性是在我的类Model中定义的属性,以及关键属性(请参阅下面的答案):
class问题(db.Model):
text = db.StringProperty()
answers = db.StringListProperty()
user = db.UserProperty()
datetime = db.DateTimeProperty()
我可以很好地访问文本,答案,用户,日期时间和键属性。但是,我无法访问ID属性。
例如,在获取所有实体(使用Question.all())之后:
#OK在模板中,这将返回一个字符串:
{{question.text}}
#OK,这将返回实体键:
{{question.key}}
#KO这将不会返回任何想法?
{{question.id}}
感谢!
根据 docs / python / datastore / modelclass.htmlrel =noreferrer> documentation ,没有为模型定义的 id()
实例方法 尝试 {{question.key}}
。
另请注意,直到实体保存到数据存储区时才会创建密钥。
编辑:更多信息基于OP的编辑:
因为我们真的在数字ID 之后,我们可以在模板中做这样的事情:
{{question.key.id}}
另一个注意事项:您不应该期望数字ID的增加与创建实体的顺序相对应。实际上,这通常是 - 但并非总是如此。
Using Google App Engine SDK and Python, I'm facing an issue : I'm unable to access the ID property of a given entity properties. The only properties I can access are those defined in my class Model, plus the key property (see answer below) :
class Question(db.Model):
text = db.StringProperty()
answers = db.StringListProperty()
user = db.UserProperty()
datetime = db.DateTimeProperty()
I can access text, answers, user, datetime and key properties just fine. However, I can't access the ID property. For example, after fetching all entities (using Question.all()) :
# OK Within a template, this will return a string :
{{ question.text }}
# OK, this will return the entity key :
{{ question.key }}
# KO this will return nothing :
{{ question.id }}
Any ideas ? Thanks !
According to the documentation, there is no id()
instance method defined for Model subclasses.
Try {{ question.key }}
instead.
Also note that the key is not created until the entity is saved to the datastore.
Edit: more info based on OP's edit:
Since we're really after the numeric ID, we could do something like this in our template:
{{ question.key.id }}
Another note: you should never expect numeric IDs to increase in value corresponding with the order of entity creation. In practice, this is usually—but not always—the case.
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