django:根据条件排除某些表单元素

Question

我有一些表单字段,我想根据是否满足某个条件来包含/排除.我知道如何包含和排除表单元素,但是当我希望它根据函数的结果显示元素时,我很难做到.

这是我的表格:

class ProfileForm(ModelForm):
    # this_team = get Team instance from team.id passed in
    # how?

    def draft_unlocked(self):
        teams = Team.objects.order_by('total_points')
        count = 0
        for team in teams:
            if team.pk == this_team.pk:
                break
            count += 1

        now = datetime.datetime.now().weekday()
        if now >= count:
            # show driver_one, driver_two, driver_three
        else:
            # do not show driver_one, driver_two, driver_three

class Meta:
    model = Team

我想要完成的是,根据总积分的排名,团队不应该在指定的日期之前改变他们的驾驶员.在比赛中,排名最后一支球队可以在周一添加/减少一名车手,倒数第二支球队可以在周二增加/减少,依此类推......

所以第一个问题 - 如何从传入的id中获取表单内部的Team实例.而且,如何根据draft_unlocked()的结果包含/排除.

或者也许有更好的方法来做所有这些？

非常感谢大家.

Answer 1

这实际上相当简单(条件字段设置) - 这是一个简单的例子:

from django.forms import Modelform
from django.forms.widgets import HiddenInput

class SomeForm(ModelForm):

    def __init__(self, *args, **kwargs):
        # call constructor to set up the fields. If you don't do this 
        # first you can't modify fields.
        super(SomeForm, self).__init__(*args, **kwargs)

        try:
            # make somefunc return something True
            # if you can change the driver.
            # might make sense in a model?
            canchangedriver = self.instance.somefunc()                          
        except AttributeError:
            # unbound form, what do you want to do here?
            canchangedriver = True # for example?

        # if the driver can't be changed, use a input=hidden
        # input field.
        if not canchangedriver:
            self.fields["Drivers"].widget = HiddenInput()

    class Meta:
        model = SomeModel

那么,关键点是:

• self.instance如果表单已绑定,则表示绑定对象.我相信它作为一个命名参数传入,因此在kwargs父构造函数用来创建self.instance.
• 您可以在调用父构造函数后修改字段属性.
• 窗口小部件是表单的显示方式.HiddenInput基本上意味着<input type="hidden" .../>.

有一个限制; 如果修改提交的POST/GET数据,我可以篡改输入以更改值.如果您不希望发生这种情况,需要考虑的事项是覆盖表单的验证(clean())方法.请记住,Django中的所有内容都只是对象,这意味着您可以实际修改类对象并随机添加数据(虽然它不会被保留).所以,__init__你可以:

self.instance.olddrivers = instance.drivers.all()

然后在你的表格的干净方法:

def clean(self):
    # validate parent. Do this first because this method
    # will transform field values into model field values.
    # i.e. instance will reflect the form changes.
    super(SomeForm, self).clean()

    # can we modify drivers?
    canchangedriver = self.instance.somefunc() 

    # either we can change the driver, or if not, we require 
    # that the two lists are, when sorted, equal (to allow for 
    # potential non equal ordering of identical elements).

    # Wrapped code here for niceness
    if (canchangedriver or 
                   (sorted(self.instance.drivers.all()) == 
                    sorted(self.instance.olddrivers))):  
        return True
    else:
        raise ValidationError() # customise this to your liking.