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How to set default values ​​for manytomanyfield

Is there an “instance must have primary key value before using many-to-many” error?

I have a model with several fields, including a many-to-many relationship to another model. I have a function to set default values ​​for these fields when I create a new instance of the model. I do this in a view when processing HTTP GET. The m2m field is displayed using a set of forms.

Here are some pseudo codes describing the situation:

class MyRelatedModel(models.Model):
  name = models.CharField(max_length=100,blank=True)

class MyModel(models.Model):
  name = models.CharField(max_length=100,blank=True)
  relatedModels = models.ManyToManyField("MyRelatedModel")

  def initialize(self):
    self.name = "my default name"
    # this bit doesn't really matter...
    # just assume I am creating a new set of RelatedModels that I want to associate with my this new MyModel...
    newRelatedModels = []
    for name in ["related model 1", "related model 2", "related model 3"]:
      relatedModel = MyRelatedModel(name=name)
      relatedModel.save()
      newRelatedModels.append(relatedModel.id)
    self.relatedModels = newRelatedModels # this is invalid!

def MyView(request):
  if request.method == 'GET':
    model = MyModel()
    model.initialize()
    form = MyForm(instance=model)
  return render_to_response("my_template.html", {"form" : form}, context_instance=RequestContext(request))

Any suggestions?

I suspect that I may need to handle this on the form side, and not on the model side, but that bothers me too.

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2

, 1.3.1:

- , inital

hardcode:

def MyView(request):
    if request.method == 'GET':
        model   = MyModel( name = "my default name")
        initial = { 'relatedModels': [1,] } # assuming you knew the id and wanted to hardcode it
        form = MyForm( instance=model, initial=initial )
        return render_to_response("my_template.html", {"form" : form}, context_instance=RequestContext(request))

:

def MyView(request):
    if request.method == 'GET':
        model   = MyModel( name = "my default name")
        initial = { 'relatedModels':  [ o.pk for o in list(MyRelatedModel.objects.filter( name__in=("related model 1", "related model 2", "related model 3")))], } 
        form = MyForm( instance=model, initial=initial )
        return render_to_response("my_template.html", {"form" : form}, context_instance=RequestContext(request))
+2
for name in ["related model 1", "related model 2", "related model 3"]:
    relatedModel = MyRelatedModel(name=name)
    relatedModel.save()
    self.relatedModels.add(relatedModel)

:

newRelatedModels = []
for name in ["related model 1", "related model 2", "related model 3"]:
    relatedModel = MyRelatedModel(name=name)
    relatedModel.save()
    newRelatedModels.append(relatedModel)
self.relatedModels.add(*newRelatedModels)

:

self.relatedModels = newRelatedModels
+1

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