背景：同一个模块，两组开发人员对同一个模型的form视图进行了二开。在没有指定外部ID的情况下，odoo是如何选择展示展示哪个视图呢？

上干货

1. odoo在加载视图的时候，首先调用的models.py中的load_views函数；

   @api.model
   def load_views(self, views, options=None):
       """ Returns the fields_views of given views, along with the fields of
           the current model, and optionally its filters for the given action.
   :param views: list of [view_id, view_type]
   :param options['toolbar']: True to include contextual actions when loading fields_views
   :param options['load_filters']: True to return the model's filters
   :param options['action_id']: id of the action to get the filters
   :return: dictionary with fields_views, fields and optionally filters
   """
   options = options or {}
   result = {}
   
   toolbar = options.get('toolbar')
   result['fields_views'] = {
       v_type: self.fields_view_get(v_id, v_type if v_type != 'list' else 'tree',
                                    toolbar=toolbar if v_type != 'search' else False)
       for [v_id, v_type] in views
   }
   result['fields'] = self.fields_get()
   
   if options.get('load_filters'):
       result['filters'] = self.env['ir.filters'].get_filters(self._name, options.get('action_id'))
   
   return result</code></pre></li>
   上面的核心在fields_view_get函数，如下，截取重要的内容
   @api.model
   
      def fields_view_get(self, view_id=None, view_type='form', toolbar=False, submenu=False):
   
          self.check_access_rights('read')
   
          view = self.env['ir.ui.view'].sudo().browse(view_id)
      # Get the view arch and all other attributes describing the composition of the view
      result = self._fields_view_get(view_id=view_id, view_type=view_type, toolbar=toolbar, submenu=submenu)
      ···
   检查权限通过后，调用_fields_view_get函数，若用户调用的视图没有指定视图ID，那么将调用默认的视图
   @api.model
   def _fields_view_get(self, view_id=None, view_type='form', toolbar=False, submenu=False):
       View = self.env['ir.ui.view'].sudo()
       result = {
           'model': self._name,
           'field_parent': False,
       }
   # try to find a view_id if none provided
   if not view_id:
       # &lt;view_type&gt;_view_ref in context can be used to overrride the default view
       view_ref_key = view_type + '_view_ref'
       view_ref = self._context.get(view_ref_key)
       if view_ref:
           if '.' in view_ref:
               module, view_ref = view_ref.split('.', 1)
               query = "SELECT res_id FROM ir_model_data WHERE model='ir.ui.view' AND module=%s AND name=%s"
               self._cr.execute(query, (module, view_ref))
               view_ref_res = self._cr.fetchone()
               if view_ref_res:
                   view_id = view_ref_res[0]
           else:
               _logger.warning('%r requires a fully-qualified external id (got: %r for model %s). '
                   'Please use the complete `module.view_id` form instead.', view_ref_key, view_ref,
                   self._name)
   
       if not view_id:
           # otherwise try to find the lowest priority matching ir.ui.view
           view_id = View.default_view(self._name, view_type)
   
   if view_id:
       # read the view with inherited views applied
       root_view = View.browse(view_id).read_combined(['id', 'name', 'field_parent', 'type', 'model', 'arch'])
       result['arch'] = root_view['arch']
       result['name'] = root_view['name']
       result['type'] = root_view['type']
       result['view_id'] = root_view['id']
       result['field_parent'] = root_view['field_parent']
       result['base_model'] = root_view['model']
   else:
       # fallback on default views methods if no ir.ui.view could be found
       try:
           arch_etree = getattr(self, '_get_default_%s_view' % view_type)()
           result['arch'] = etree.tostring(arch_etree, encoding='unicode')
           result['type'] = view_type
           result['name'] = 'default'
       except AttributeError:
           raise UserError(_("No default view of type '%s' could be found !", view_type))
   return result</code></pre></li>
   此处我们讨论的是odoo是如何取默认视图的，再进ir.ui.view模型的default_view函数查看
   @api.model
   def default_view(self, model, view_type):
       """ Fetches the default view for the provided (model, view_type) pair:
        primary view with the lowest priority.
   :param str model:
   :param int view_type:
   :return: id of the default view of False if none found
   :rtype: int
   """
   domain = [('model', '=', model), ('type', '=', view_type), ('mode', '=', 'primary')]
   return self.search(domain, limit=1).id</code></pre></li>
   是不是很惊喜，毛都没有，看不出来如何做的选择。别着急，看ir.ui.view的模型吧。  
   
   

有点坑啊，大家在视图继承的时候。权重基本上是默认的，也就是说若不考虑name的影响，那么默认视图将永远是最先添加的基础视图。但是，这里name的排序居然还在ID的前面，这就有的玩了嘛，起名字也是门艺术了。

1. 好了回归正题，在步骤3中，拿到了默认视图后，我们取到的视图有可能是继承视图，也有可能是基础视图。那么将通过read_combined函数拼接出来以基础视图为框架，包含所有继承视图内容的etree对象。

   def read_combined(self, fields=None):
       """
       Utility function to get a view combined with its inherited views.
   * Gets the top of the view tree if a sub-view is requested
   * Applies all inherited archs on the root view
   * Returns the view with all requested fields
     .. note:: ``arch`` is always added to the fields list even if not
               requested (similar to ``id``)
   """
   # introduce check_view_ids in context
   if 'check_view_ids' not in self._context:
       self = self.with_context(check_view_ids=[])
   
   check_view_ids = self._context['check_view_ids']
   
   # if view_id is not a root view, climb back to the top.
   root = self
   while root.mode != 'primary':
       # Add inherited views to the list of loading forced views
       # Otherwise, inherited views could not find elements created in their direct parents if that parent is defined in the same module
       check_view_ids.append(root.id)
       root = root.inherit_id
   
   # arch and model fields are always returned
   if fields:
       fields = list({'arch', 'model'}.union(fields))
   
   # read the view arch
   [view_data] = root.read(fields=fields)
   view_arch = etree.fromstring(view_data['arch'].encode('utf-8'))
   if not root.inherit_id:
       if self._context.get('inherit_branding'):
           view_arch.attrib.update({
               'data-oe-model': 'ir.ui.view',
               'data-oe-id': str(root.id),
               'data-oe-field': 'arch',
           })
       arch_tree = view_arch
   else:
       if self._context.get('inherit_branding'):
           root.inherit_branding(view_arch)
       parent_view = root.inherit_id.read_combined(fields=fields)
       arch_tree = etree.fromstring(parent_view['arch'])
       arch_tree = self.browse(parent_view['id']).apply_inheritance_specs(arch_tree, view_arch)
   
   # and apply inheritance
   arch = root.apply_view_inheritance(arch_tree, self.model)
   
   return dict(view_data, arch=etree.tostring(arch, encoding='unicode'))</code></pre></li>

结束