使用元组时，ChoiceField 不显示空标签 [英] ChoiceField doesn't display an empty label when using a tuple

问题描述

我将在我的数据库中保存有关比赛的数据.我希望能够按特定条件搜索比赛 - 特别是比赛类型.

I'm going to be keeping data about competitions in my database. I want to be able to search the competitions by certain criteria - competition type in particular.

竞争类型保存在一个元组中.一个稍微缩短的例子:

Competition types are kept in a tuple. A slightly shortened example:

COMPETITION_TYPE_CHOICES = (
    (1, 'Olympic Games'),
    (2, 'ISU Championships'),
    (3, 'Grand Prix Series'),
)

这些在模型中像这样使用(再次 - 这是模型的缩短/简化版本):

These are used in the model like so (again - this is a shortened/simplified version of the model):

class Competition(models.Model):
    name = models.CharField(max_length=256)
    type = models.IntegerField(choices=COMPETITION_TYPE_CHOICES) 

搜索表单

我不希望搜索表单中的字段是必需的，因此表单定义如下:

The search form

I don't want the fields to be required in the search form, so the form is defined like this:

class CompetitionSearchForm(forms.Form):
    name = forms.CharField(required=False)
    type = forms.ChoiceField(choices=COMPETITION_TYPE_CHOICES,required=False)

问题

我希望 ChoiceField 中的选择小部件显示一个空标签，但我没有找到.对此的任何帮助将不胜感激:)

The problem

I'd like the select widget in ChoiceField to display an empty label, but I don't get one. Any help with this would be much appreciated :)

推荐答案

我找到了一种解决方案，它可以按照我希望的方式工作，而且不会违反 DRY 原则.不是很干净，但我想应该可以.

I've found a solution that works the way I want it to without violating the DRY principle. Not very clean, but it'll have to do I suppose.

根据文档 选择没有成为一个元组:

According to the documentation choices don't have to be a tuple:

最后，请注意选择可以是任何可迭代对象——不一定是列表或元组.这使您可以构建动态选择.但是如果你发现你自己的黑客选择动态的，你可能会更好使用适当的数据库表外键.选择是为了变化不大的静态数据，如果有的话.

Finally, note that choices can be any iterable object -- not necessarily a list or tuple. This lets you construct choices dynamically. But if you find yourself hacking choices to be dynamic, you're probably better off using a proper database table with a ForeignKey. choices is meant for static data that doesn't change much, if ever.

所以我目前的解决方案是:

So the solution I'm going with for the moment is:

COMPETITION_TYPE_CHOICES = [
     (1, 'Olympic Games'),
     (2, 'ISU Championships'),
     (3, 'Grand Prix Series'),
]

COMP_TYPE_CHOICES_AND_EMPTY = [('','All')] + COMPETITION_TYPE_CHOICES

然后:

class CompetitionSearchForm(forms.Form):
    name = forms.CharField(required=False)
    type = forms.ChoiceField(choices=COMP_TYPE_CHOICES_AND_EMPTY, required=False)

模型保持不变.

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