使用元组时，ChoiceField不会显示空标签 - 我做错了什么？ [英] ChoiceField doesn't display an empty label when using a tuple - am I doing something wrong?

问题描述

我要做的是

我将在数据库中保留有关比赛的数据。我想能够通过某些标准来搜索比赛 - 特别是比赛类型。

关于比赛类型

比赛类型保存在元组中。稍微缩短的例子：

  COMPETITION_TYPE_CHOICES =（
（1，奥运），
 2，ISU锦标赛），
（3，大奖赛系列），
）
  

这些在模型中使用（再次 - 这是模型的缩写/简化版本）：

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

搜索表单

我不想在搜索表单中要求字段，所以表单定义如下：

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

< h2>问题

我想要ChoiceField中的选择小部件disp放一个空的标签，但我不会得到一个。对此的任何帮助将非常感谢：）

解决方案

我找到了一种解决方案，违反DRY原则。不太干净，但是我想这样做。

根据文档的选择不一定是元组：

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。这样可以动态构建
选项。但是如果你发现
你自己的黑客选择是
的动态，你可能会更好的
使用正确的数据库表与
ForeignKey。选择是为
静态数据变化不大，
如果有的话。

所以解决方案我现在要去的是：

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

然后：

<$
name = forms.CharField（required = False）
type = forms.ChoiceField（choices = COMP_TYPE_CHOICES_AND_EMPTY，required = False）p $ p> class CompetitionSearchForm（forms.Form）


模型保持不变。

What I'm trying to do

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.

About competition types

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

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

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) 

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)

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 :)

解决方案

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.

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

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.

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

And then:

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

The model stays the same as it was.

这篇关于使用元组时，ChoiceField不会显示空标签 - 我做错了什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！