Creating a dynamic choice field

Question

I m having some trouble trying to understand how to create a dynamic choice field in django  I have a model set up something like   class rider models Model        user   models ForeignKey User       waypoint   models ManyToManyField Waypoint   class Waypoint models Model        lat   models FloatField        lng   models FloatField     What I m trying to do is create a choice Field whos values are the waypoints associated with that rider  which would be the person logged in    Currently I m overriding init in my forms like so   class waypointForm forms Form        def   init   self   args    kwargs             super joinTripForm  self    init    args    kwargs            self fields  waypoints     forms ChoiceField choices    o id  str o   for o in Waypoint objects all       But all that does is list all the waypoints  they re not associated with any particular rider  Any ideas  Thanks

User · Answer

Underneath working solution with normal choice field  my problem was that each user have their own CUSTOM choicefield options based on few conditions   class SupportForm BaseForm        affiliated   ChoiceField required False  label  Fieldname   choices     widget Select attrs   onchange    sysAdminCheck             def   init   self   args    kwargs            self request   kwargs pop  request   None          grid id   get user from request self request          for l in get all choices   filter user user id               admin    y  if l in self core else  n              choice       s  s     l name  admin       s    l name               self affiliated choices append choice          super SupportForm  self    init    args    kwargs          self fields  affiliated   choices   self affiliated choice

User · Answer

you can filter the waypoints by passing the user to the form init  class waypointForm forms Form       def   init   self  user   args    kwargs           super waypointForm  self    init    args    kwargs          self fields  waypoints     forms ChoiceField              choices   o id  str o   for o in Waypoint objects filter user user               from your view while initiating the form pass the user  form   waypointForm user    in case of model form  class waypointForm forms ModelForm       def   init   self  user   args    kwargs           super waypointForm  self    init    args    kwargs          self fields  waypoints     forms ModelChoiceField              queryset Waypoint objects filter user user                 class Meta          model   Waypoint

User · Answer

the problem is when you do  def   init   self  user   args    kwargs       super waypointForm  self    init    args    kwargs      self fields  waypoints     forms ChoiceField choices    o id  str o   for o in Waypoint objects filter user user      in a update request  the previous value will lost

User · Answer

You can declare the field as a first-class attribute of your form and just set choices dynamically   class WaypointForm forms Form       waypoints   forms ChoiceField choices          def   init   self  user   args    kwargs           super     init    args    kwargs          waypoint choices     o id  str o   for o in Waypoint objects filter user user           self fields  waypoints   choices   waypoint choices   You can also use a ModelChoiceField and set the queryset on init in a similar manner

User · Answer

As pointed by Breedly and Liang  Ashok s solution will prevent you from getting the select value when posting the form   One slightly different  but still imperfect  way to solve that would be   class waypointForm forms Form       def   init   self  user   args    kwargs           self base fields  waypoints   choices   self  do the choicy thing           super waypointForm  self    init    args    kwargs    This could cause some concurrence problems  though

User · Answer

If you need a dynamic choice field in django admin  This works for django   2 1   class CarAdminForm forms ModelForm       class Meta          model   Car      def   init   self   args    kwargs           super CarForm  self    init    args    kwargs             Now you can make it dynamic          choices                   audi    Audi                  tesla    Tesla                      self fields get  car field   choices   choices      car field   forms ChoiceField choices       admin register Car  class CarAdmin admin ModelAdmin       form   CarAdminForm   Hope this helps

User · Answer

How about passing the rider instance to the form while initializing it   class WaypointForm forms Form       def   init   self  rider   args    kwargs         super joinTripForm  self    init    args    kwargs        qs   rider Waypoint set all         self fields  waypoints     forms ChoiceField choices   o id  str o   for o in qs      In view  rider   request user form   WaypointForm rider

User · Answer

There s built-in solution for your problem  ModelChoiceField   Generally  it s always worth trying to use ModelForm when you need to create change database objects   Works in 95  of the cases and it s much cleaner than creating your own implementation

[python] Creating a dynamic choice field

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