返回Django模型上的空字段的默认值 [英] return a default value for empty field on a django model

问题描述

我有一个模型，其中一个字段通常是空白字符串.有没有办法返回(例如)字符串"default"而不是该模型查询的空白字符串?

I have a model in which one field is often the blank string. Is there a way to return (for e.g.) the string 'default' instead of that blank string for queries on that model?

class MyModel(models.Model):
    ...
    afield = models.CharField(...)  # many rows set afield to ''

我执行查询时

o = MyModel.objects.all()
vars(o[0])
{...
'afield': ''  # afield is empty
...}

我宁愿

vars(o[0])
{...
'afield': 'default'
...}

有没有办法做到这一点?有没有比在模型内部更好的方法呢?

Is there a way to do this? Is there a better way to implement this than inside the model?

注意:

• 我不想存储字符串'default'
• 此答案更改了数据库，我想避免这种情况

• I do not want to store the string 'default'
• this answer alters the database, I want to avoid that

推荐答案

在视图中将其作为逻辑的一部分来处理可能更好，很多，很多，但是您可以使用属性和设置器来做到这一点:

It is probably much, much, much better to handle this in views as part of your logic, but you could use properties and setters to do this:

class MyModel(models.Model):
    _afield = models.CharField(...)
    @property
    def afield(self):
        if self._afield:
            return self._afield
        else:
            return "default"

    @afield.setter
    def afield_setter(self,value):
        self._afield = value

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