#

# Licensed to the Apache Software Foundation (ASF) under one or more

# contributor license agreements. See the NOTICE file distributed with

# this work for additional information regarding copyright ownership.

# The ASF licenses this file to You under the Apache License, Version 2.0

# (the "License"); you may not use this file except in compliance with

# the License. You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

#

"""Observable base class for iterables.

For internal use only; no backwards-compatibility guarantees.

"""

# pytype: skip-file

class ObservableMixin(object):

"""For internal use only; no backwards-compatibility guarantees.

An observable iterable.

Subclasses need to call self.notify_observers with any object yielded.

"""

def __init__(self):

self.observers = []

def register_observer(self, callback):

self.observers.append(callback)

def notify_observers(self, value, **kwargs):

# self.observers is almost always empty

if self.observers:

for o in self.observers:

o(value, **kwargs)