Question

我正在寻找Python中的通用方法，通过其名称实例化类，就像在Java中完成它一样，而不必在IF..ELIF条件中明确指定类名。

这是因为我有几个不同的模型和序列化器，并希望通过HTTP请求中的参数使它们可寻址。它是为了增强松耦合和模块化。

例如https://www.domain.com/myapp/sampledata.json?model=<modelname>应该获得课程<modelname>和<modelname>Serializer。

自从https://docs.djangoproject.com/en/1.7/ref/models/queries/用于类似目的之前，Django 1.7 get_model以来对此进行了一些更改。

从Django 1.7开始，不推荐使用django.db.models.loading（将... 在1.9）中删除了有利于新的应用程序加载系统。

警告：

RemovedInDjango19Warning：django.db.models.loading中的实用程序不赞成使用新的应用程序加载系统 return f（* args，** kwds）

如何修改以下代码以从字符串中获取类？

views.py

from myapp.models import Samplemodel, Simplemodel1, Simplemodel2
from myapp.serializers import SamplemodelSerializer, Simplemodel1Serializer, Simplemodel2Serializer
from django.db.models.loading import get_model # deprecated
from myapp.jsonp_decorator import json_response

@json_response
def sampledata(request):

    model = request.GET.get('model','Samplemodel')

    if model=='Samplemodel':
        modelName = "Samplemodel"
        serializer = SamplemodelSerializer
    elif model=='Simplemodel1':
        modelName = "Simplemodel1"
        serializer = Simplemodel1Serializer
    elif model=='Simplemodel2':
        modelName = "Simplemodel2"
        serializer = Simplemodel2Serializer

    return serializer(get_model("myapp",modelName).objects.all(), many=True)

Answer 1

您可以使用getattr：

import my_serializers

serializer_class = getattr(my_serializers, 'SimpleSerializer')
serializer = serializer_class()

Answer 2

对于Django 3+ 获取模型实例的通用方法：

def get_data_instance(model_name):
    """
    Try to find application with name "data" with specific "model_name"
    :param model_name: the name of the class
    :return: model instance or None
    """

    try:
        app_config = apps.get_app_config('data')
        return app_config.get_model(model_name)
    except LookupError:
        pass

    return None

Answer 3

在这种情况下允许动态类加载的最佳方法是：

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      <th scope="col">Task </th>
      <th scope="col">Event</th>
      <th scope="col">Date</th>
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    </tr>
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      <td>August 29, 2013</td>
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      <td>August 22, 2013</td>
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      <td>n/a</td>
    </tr>
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      <td>fghfgh</td>
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      <td>August 29, 2013</td>
      <td>
        James Bradley
      </td>
      <td>n/a</td>
    </tr>

  </tbody>
</table>

Django从字符串中获取类

3 个答案: