直接在模型中存储django forms.MultipleChoiceField [英] Store django forms.MultipleChoiceField in Models directly

问题描述

说我有如下定义的选择：

  choices =（（'1'，'a'），
（'2'，'b'），
（'3'，'c'））
  

一个表单，它在MultipleChoiceField中呈现和输入这些值，

  class Form1（forms.Form）： 
 field = forms.MultipleChoiceField（choices = choices）
  

什么是正确的存储方式

我当然可以循环使用 forms.cleaned_data [ 'field'] 并获得一个适合 models.CommaSeperatedIntegerField 的值。

再次，每次我检索这些值，我将不得不循环并转换为选项。

我认为有更好的方式这样做，因为这样，我正在重新实现CommaSeparateIntegerField应该做的功能。

解决方案

第一个薄g我会考虑更好地规范化您的数据库模式;如果您的模型的单个实例可以具有此字段的多个值，该字段可能应该是与ForeignKey的链接模型。

如果您使用Postgres，您也可以使用ARRAY字段; Django现在已经内置的支持。

如果你不能做任何一个，那么你基本上需要重新实现一个（更好的）版本的CommaSeparatedIntegerField。原因是CommaSeparatedIntegerField只是一个纯粹的CharField，其默认格式表示是正则表达式验证的文本输入。换句话说，它不会对您有用的任何事情。

您需要编写的是一个自定义的ListField或MultipleValuesField，它们期待Python列表并返回一个Python列表，但内部将该列表转换为/从逗号分隔的字符串插入数据库。请阅读有关自定义模型字段的文档;我想在你的情况下，你会想要一个CharField的子类，覆盖了两种方法： to_python （将CSV字符串转换为Python列表）和 get_db_prep_value （将Python列表转换为CSV字符串）。

Say I have choices defined as follows:

choices = (('1','a'),
           ('2','b'),
           ('3','c'))

And a form that renders and inputs these values in a MultipleChoiceField,

class Form1(forms.Form):
    field = forms.MultipleChoiceField(choices=choices)

What is the right way to store field in a model.

I can of course loop through the forms.cleaned_data['field'] and obtain a value that fits in models.CommaSeperatedIntegerField.

Again, each time I retrieve these values, I will have to loop and convert into options.

I think there is a better way to do so, as in this way, I am in a way re-implementing the function that CommaSeperateIntegerField is supposed to do.

解决方案

The first thing I would consider is better normalization of your database schema; if a single instance of your model can have multiple values for this field, the field perhaps should be a linked model with a ForeignKey instead.

If you're using Postgres, you could also use an ARRAY field; Django now has built-in support.

If you can't do either of those, then you do basically need to reimplement a (better) version of CommaSeparatedIntegerField. The reason is that CommaSeparatedIntegerField is nothing but a plain CharField whose default formfield representation is a regex-validated text input. In other words, it doesn't do anything that's useful to you.

What you need to write is a custom ListField or MultipleValuesField that expects a Python list and returns a Python list, but internally converts that list to/from a comma-separated string for insertion in the database. Read the documentation on custom model fields; I think in your case you'll want a subclass of CharField with two methods overridden: to_python (convert CSV string to Python list) and get_db_prep_value (convert Python list to CSV string).

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