python - 如何自省(introspection) django 模型字段？

Question

当我只知道字段名称和模型名称(均为纯字符串)时，我正在尝试获取模型内字段的类信息。怎么可能？

我可以动态加载模型:

from django.db import models
model = models.get_model('myapp','mymodel')

现在我有字段 - 'myfield' - 我怎样才能获得该字段的类？

如果字段是关系型 - 如何获取相关字段？

非常感谢!

Answer 1

您可以使用模型的 _meta 属性来获取字段对象，并从字段中获取关系等等，例如考虑一个员工表，它有一个部门表的外键

In [1]: from django.db import models

In [2]: model = models.get_model('timeapp', 'Employee')

In [3]: dep_field = model._meta.get_field_by_name('department')

In [4]: dep_field[0].target_field
Out[4]: 'id'

In [5]: dep_field[0].related_model
Out[5]: <class 'timesite.timeapp.models.Department'>

来自 django/db/models/options.py

def get_field_by_name(self, name):
    """
    Returns the (field_object, model, direct, m2m), where field_object is
    the Field instance for the given name, model is the model containing
    this field (None for local fields), direct is True if the field exists
    on this model, and m2m is True for many-to-many relations. When
    'direct' is False, 'field_object' is the corresponding RelatedObject
    for this field (since the field doesn't have an instance associated
    with it).

    Uses a cache internally, so after the first access, this is very fast.
    """