基于另一个模型字段的Django模型字段默认 [英] Django model field default based on another model field

问题描述

我使用Django Admin建立管理网站。有两个表，一个是 ModelA ，其中包含数据，另一个是 ModelB ，其中没有任何内容。如果 ModelB 中的一个模型字段 b_b 为None，则可以显示在值为<$ c的网页上$ c> ModelA 的字段 a_b 。

I use Django Admin to build a management site. There are two tables, one is ModelA with data in it, another is ModelB with nothing in it. If one model field b_b in ModelB is None, it can be displayed on the webpage with the value of ModelA's field a_b.

我不知道要做到这一点，这是伪代码：

I don't know how to do it, Here is the pseudo code:

在models.py

In models.py

from django.db import models

class ModelA(models.Model):
  a_a = models.CharField(max_length=6)
  a_b = models.CharField(max_length=6)

class ModelB(models.Model):
  modela = models.OneToOneField(ModelA)
  b_b = models.CharField(max_length=6, choices=[(1, 'M'), (2, 'F')], default=self.modela.a_b)

在admin.py

from django.contrib import admin
from .models import ModelA, ModelB

class ModelBAdmin(admin.ModelAdmin):
  fields = ['b_b']
  list_display = ('b_b')

我想如果modelB的b_b的默认值为relative a_b value在modelA中，我在django管理员更改（编辑）页面中有一个默认值b_b（View），它将数据与特定的modelB实例相关联。

I think if b_b of modelB have default value of relative a_b value of modelA, I have a default value of b_b(View) in the django admin change(edit) page which associate data to a particular modelB instance.

我想在网页中更容易填写b_b。

I want to fill b_b in web page more easily.

我不知道这个要求是否可以实现？还有另一种方法可以实现这一点？

I don't know whether this requirement can be achieved? Or there is another way can achieve this?

我尝试自定义模板过滤器如下：

I try to custom the templates filter as following:

template / admin / includes / fieldset.html

In templates/admin/includes/fieldset.html

 {% load drop_null %}

    {% if field.is_checkbox %}
        {{ field.field }}{{ field.label_tag }}
    {% else %}
        {{ field.label_tag }}
        {% if field.is_readonly %}
            <p>{{ field.contents }}</p>
        {% else %}
            {% if field.field.name == 'b_b' %}
                {{ field|dropnull }}
            {% else %}
                {{ field.field }}
            {% endif %}
        {% endif %}
    {% endif %}

在模板标签/ drop_null.py

In templatetags/drop_null.py

from django import template
register = template.Library()

@register.filter(name='dropnull')
def dropnull(cls):
    return cls.modela.a_b

'field'是< django.contrib.admin.helpers.AdminField对象在0x3cc3550>。它不是ModelB的一个实例。
如何获取ModelB实例？

The 'field' is < django.contrib.admin.helpers.AdminField object at 0x3cc3550> . It is not an instance of ModelB. How can I get ModelB instance?

推荐答案

您可以覆盖 save modelB 模型的c $ c>方法，而不是提供默认值：

You can override the save method of your modelB model instead of providing a default value:

class ModelB(models.Model):
    modela = models.OneToOneField(ModelA)
    b_b = models.CharField(max_length=6, choices=[(1, 'M'), (2, 'F')], blank=True)

    def save(self, *args, **kwargs):
        if not self.b_b:
            self.b_b = self.modela.a_b
        super(ModelB, self).save(*args, **kwargs)

---

在评论中澄清后编辑

如果您只想向参观者显示价值，但想保留事实上， ModelB.b_b 是空的，逻辑应该放在模板中。

---

Edit after clarification in the comments

If you just want to display the value to visitors but want to keep the fact that the ModelB.b_b is empty, the logic should lay in the template.

假设你的视图集 objB 在上下文中，您有兴趣显示的 ModelB 对象，相关模板的一部分应该如下所示：

Assuming your view set objB in the context being the ModelB object your are interested to display, the relevant part of the template should look like:

{% with objB.b_b as bValue %}
{% if not bValue %}
    <p>{{ objB.modela.a_b }}</p>
{% else %}
    <p>{{ bValue }}</p>
{% endif %}
{% endwith %}

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