如何設置默認值爲manytomanyfield

Question

有沒有解決方法「實例需要有一個主鍵值之前，可以使用多對多關係」的錯誤？

我有一個模型有幾個字段，包括與另一個模型的多對多關係。當我創建模型的新實例時，我有一個函數可以在這些字段上設置默認值。處理HTTP GET時，我在視圖中執行此操作。 m2m字段使用formset呈現。

這裏描述的情況有些僞代碼：

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)) 

有什麼建議？

我懷疑我可能需要在表單一側而不是模型一側處理這個問題，但這也讓我感到困惑。

Answer 1

對於什麼是1.3.1爲我工作的形式：

是類似於此，inital的許多東西

用硬編碼標識：

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)) 

使用查詢通過名稱來填充：

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)) 

Answer 2

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

或者：

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) 

這應該工作太：

self.relatedModels = newRelatedModels