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

2. 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)
       ···

3. 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:
            # <view_type>_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

4. 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

5. 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。

6. 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'))

结束