Method position_instance_for

flows/handler.py:422–462

(self, component_class_or_name)

            return '%(root)s%(url)s' % { 'root': config.FLOWS_SITE_ROOT, 'url': url }

    def position_instance_for(self, component_class_or_name):
        # figure out where we're being sent to
        FC = get_by_class_or_name(component_class_or_name)
        
        # it should be a sibling of one of the current items
        # for example, if we are in position [A,B,E]:
        #
        #         A
        #      /  |  \
        #    B    C   D
        #   /  \      |  \
        #  E   F      G   H
        # 
        #  E can send to F (its own sibling) or C (sibling of its parent)

        for fci in self._flow_components[-2::-1]: # go backwards but skip the last element (the action)
            if FC in fci.action_set:
                # we found the relevant action set, which means we know the root
                # part of the tree, and now we can construct the rest
                idx = self._flow_components.index(fci)
                break
        else:
            raise ValueError('Could not figure out how to redirect to %s' % FC)

        # so the new tree is from the root to the parent of the one we just found,
        # coupled with the initial subtree from the component we're tring to redirect
        # to
        tree_root = self._position.flow_component_classes[:idx+1]
        
        # figure out the action tree for the new first component - either
        # we have been given an action, in which case it's just one single
        # item, or we have been given a scaffold, in which case there could
        # be a list of [scaffold, scaffold..., action]
        new_subtree = FC.get_initial_action_tree()
        
        # we use our current tree and replace the current leaf with this new 
        # subtree to get the new position
        new_position = PossibleFlowPosition(self._app_namespace, self._flow_namespace, tree_root + new_subtree)
        
        # now create an instance of the position with the current state
        return new_position.create_instance(self._state, self.state_store, self._url_args, self._url_kwargs)
    
    def handle(self, request, *args, **kwargs):
        # first validate that we can actually run by checking for