當反向關係中full = True時，Django Tastypie會拋出'超出最大遞歸深度'。

Question

我得到，如果運行下面的代碼超過最大遞歸深度：

from tastypie import fields, utils 
from tastypie.resources import ModelResource 
from core.models import Project, Client 


class ClientResource(ModelResource): 
    projects = fields.ToManyField(
     'api.resources.ProjectResource', 'project_set', full=True 
    ) 
    class Meta: 
     queryset = Client.objects.all() 
     resource_name = 'client' 


class ProjectResource(ModelResource): 
    client = fields.ForeignKey(ClientResource, 'client', full=True) 
    class Meta: 
     queryset = Project.objects.all() 
     resource_name = 'project' 

# curl http://localhost:8000/api/client/?format=json 
# or 
# curl http://localhost:8000/api/project/?format=json 

如果一套全=假在它工作的關係之一。我明白爲什麼會發生這種情況，但我需要兩種關係才能提供數據，而不僅僅是「resource_uri」。是否有Tastypie的方式來做到這一點？我設法解決了在我的項目模型中創建序列化方法的問題，但它遠非優雅。謝謝。

Answer 1

您必須在至少一個資源上覆蓋full_dehydrate方法以跳過導致遞歸的相關資源脫水。

或者，您可以定義兩種類型的資源，使用full=True和full=False中的一個模型。

Answer 2

謝謝@astevanovic指向正確的方向。

我發現重寫dehydrate方法來處理只有一些指定的字段比重寫full_hydrate方法略過繁瑣，以略過字段。

爲了追求可重用性，我想出了以下代碼片段。希望這將是有用的一些：

class BeeModelResource(ModelResource): 

    def dehydrate(self, bundle): 
     bundle = super(BeeModelResource, self).dehydrate(bundle) 
     bundle = self.dehydrate_partial(bundle)   
     return bundle 

    def dehydrate_partial(self, bundle): 
     for field_name, resource_field in self.fields.items(): 
      if not isinstance(resource_field, RelatedField): 
       continue 

      if resource_field.full: # already dehydrated 
       continue 

      if not field_name in self._meta.partial_fields: 
       continue 

      if isinstance(resource_field, ToOneField): 
       fk_object = getattr(bundle.obj, resource_field.attribute) 
       fk_bundle = Bundle(obj=fk_object, request=bundle.request) 
       fk_resource = resource_field.get_related_resource(fk_object) 

       bundle.data[field_name] = fk_resource.dehydrate_selected( 
         fk_bundle, self._meta.partial_fields[field_name]).data 
      elif isinstance(resource_field, ToManyField): 
       data = [] 

       fk_objects = getattr(bundle.obj, resource_field.attribute) 
       for fk_object in fk_objects.all(): 
        fk_bundle = Bundle(obj=fk_object, request=bundle.request) 
        fk_resource = resource_field.get_related_resource(fk_object) 
        fk_bundle = fk_resource.dehydrate_selected_fields( 
          fk_bundle, self._meta.partial_fields[field_name]) 
        data.append(fk_bundle.data) 
       bundle.data[field_name] = data 

     return bundle 

    def dehydrate_selected_fields(self, bundle, selected_field_names): 
     # Dehydrate each field. 
     for field_name, field_object in self.fields.items(): 
      # A touch leaky but it makes URI resolution work. 
      # (borrowed from tastypie.resources.full_dehydrate) 
      if field_name in selected_field_names and not self.is_special_fields(field_name): 
       if getattr(field_object, 'dehydrated_type', None) == 'related': 
        field_object.api_name = self._meta.api_name 
        field_object.resource_name = self._meta.resource_name 

       bundle.data[field_name] = field_object.dehydrate(bundle) 

     bundle.data['resource_uri'] = self.get_resource_uri(bundle.obj) 
     bundle.data['id'] = bundle.obj.pk 

     return bundle 

    @staticmethod 
    def is_special_fields(field_name): 
     return field_name in ['resource_uri'] 

隨着@sigmus'例如，資源將需要3次修改：

1. 資源都將使用BeeModuleResource作爲它的超類（或加dehydrate_partial一個資源和dehydrate_selected其他。）
2. 在任一資源未設置full=True
3. 添加partial_fields到資源Meta未凝固的資源

```

class ClientResource(BeeModelResource): # make BeeModelResource a super class 
    projects = fields.ToManyField(
     'api.resources.ProjectResource', 'project_set' 
    ) # remove full=True 
    class Meta: 
     queryset = Client.objects.all() 
     resource_name = 'client' 
     partial_fields = {'projects': ['memo', 'title']} # add partial_fields 

class ProjectResource(BeeModelResource): # make BeeModelResource a super class 
    client = fields.ForeignKey(ClientResource, 'client', full=True) 
    class Meta: 
     queryset = Project.objects.all() 
     resource_name = 'project' 

Answer 3

死簡單的解決方案：設置use_in = 'list' kwarg雙方關係領域！

文檔：http://django-tastypie.readthedocs.org/en/latest/fields.html#use-in