Adding _Future type for storage batches.

gcloud/storage/batch.py

@@ -71,6 +71,40 @@ class NoContent(object):
     status = 204
 
 
+class _Future(object):
+    """Class to hold a future value for a deferred request.
+
+    Used by for requests that get sent in a :class:`Batch`.
+    """
+
+    def __init__(self):
+        self._value = None
+
+    def get_value(self):
+        """Gets the value associated with the future.
+
+        :rtype: object
+        :returns: The future value that was set.
+        :raises: :class:`ValueError` if the value has not been set.
+        """
+        if self._value is None:
+            raise ValueError('Future value is unset.')
+        return self._value
+
+    def set_value(self, value):
+        """Sets the value associated with the future.
+
+        :type value: object
+        :param value: The future value that was set.
+
+        :raises: :class:`ValueError` if the value is already set.
+        """
+        if self._value is None:
+            self._value = value
+        else:
+            raise ValueError('Future value is already set.')
+
+
 class Batch(Connection):
     """Proxy an underlying connection, batching up change operations.