需要获取实体键来删除实体 [英] need to get entity key to delete entity

问题描述

我试图使用html中的链接从Datastore中删除一个实体。我知道为了做到这一点，我需要拥有实体的密钥，以便我知道哪个实体将删除链接配对，可以这么说。我不能为我的生活找出如何做到这一点......

I am trying to delete an entity from the Datastore using a link in html. I understand that in order to do this, I need to have the entity's key so that I know which entity to "pair" the delete link with, so to speak. I can't for the life of me figure out how to do this...

这是我的html文件，显示数据库中的所有汽车：

Here is my html file that shows all of the cars in the database:

{% if cars|length > 0 %}
        {% for c in cars %}
            <tr>
                <td>{{ c.make }}</td>
                <td>{{ c.model }}</td>
                <td>{{ c.year }}</td>
                <td>
                    {% for i in c.color %}
                        {{ i }}
                    {% endfor %}
                </td>
                <td>{{ c.condition }}</td>
                <td>{{ c.date }}</td>
                <td>
                    <a href="/view_cars/{{ c.key().id() }}">Delete Car</a>
                </td>
            </tr>
            {% endfor %}
        {% endif %}

python文件：

Here is the python file:

class AddCarHandler(webapp2.RequestHandler):
    template_variables = {}

    def get(self):
        template = JINJA_ENVIRONMENT.get_template('index.html')
        self.response.write(template.render(self.template_variables))

        action = self.request.get('action')

        #if the user adds a car
        if action == 'add_car':
            c = car_database.Car()

            c.make = self.request.get('car-make')
            c.model = self.request.get('car-model')
            c.year = self.request.get('car-year')
            c.color = self.request.get_all('car-color')
            c.condition = self.request.get('car-condition')
            c.date = self.request.get('car-date')

            car_key = c.put()

class ViewCarHandler(webapp2.RequestHandler):
    template_variables = {}

    def get(self):
        car = car_database.Car()
        #ndb query
        self.template_variables['cars'] = [{'make':x.make, 'model':x.model, 'year':x.year, 'color':x.color, 'condition':x.condition, 'date':x.date} for x in    car_database.Car.query().fetch()]
        template = JINJA_ENVIRONMENT.get_template('/view_cars.html')
        self.response.write(template.render(self.template_variables))

推荐答案

您可以像下面这样获取实体的关键字（即通过查询获得）：

You can get the key of an entity (which, say, is obtained through a query) like this:

entity_key = entity.key

注意：这仅适用于 >实体保存到数据库中，而不是之前（即 entity.put（）至少被调用一次）。

Note: this only works after the entity was saved into the DB, not before (i.e. entity.put() was called at least once).

在python代码和URL之间传递密钥或HTML代码，您可以从文档中使用密钥url字符串或基于该字符串的预先计算的删除url，例如，在 self.template_variables ['cars'] 中传递：

To pass the key between the python code and URLs or HTML code, from the documentation, you can use a key's url string or a pre-computed deletion url based on that string, passed, for example, in self.template_variables['cars']:

您也可以使用实体的密钥来获取适合
的编码字符串，以便嵌入到URL中：

You can also use an entity's key to obtain an encoded string suitable for embedding in a URL:

url_string = sandy_key.urlsafe()

结果像agVoZWxsb3IPCxIHQWNjb3VudBiZiwIM可以
以后用来重建密钥并检索原始实体：

This produces a result like agVoZWxsb3IPCxIHQWNjb3VudBiZiwIM which can later be used to reconstruct the key and retrieve the original entity:

sandy_key = ndb.Key(urlsafe=url_string)
sandy = sandy_key.get()

您需要为s添加一个处理程序你可以在上面引用这个关键字，然后调用：

You'll need to add a handler for such deletion url, in which you'd reconstruct the key as quoted above, then call:

entity_key.delete()

这篇关于需要获取实体键来删除实体的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！