Add factory helper function which returns a singleton
Not that ServiceTypes is super expensive or anything, but it's also an encapsultation of static data, so there's really no need to construct more than one of them in a program. Change-Id: I2515fd9be27421006ed22a3ab01bef8cb48196f8
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@ -18,3 +18,24 @@ import pbr.version
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from os_service_types.service_types import ServiceTypes # flake8: noqa
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from os_service_types.service_types import ServiceTypes # flake8: noqa
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__version__ = pbr.version.VersionInfo('os-service-types').version_string()
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__version__ = pbr.version.VersionInfo('os-service-types').version_string()
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_service_type_manager = None
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def get_service_types(*args, **kwargs):
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"""Return singleton instance of the ServiceTypes object.
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Parameters are all passed through to the
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:class:`~os_service_types.service_types.ServiceTypes` constructor.
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.. note::
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Only one singleton is kept, so if instances with different parameter
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values are desired, directly calling the constructor is necessary.
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:returns: Singleton instance of
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:class:`~os_service_types.service_types.ServiceTypes`
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"""
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global _service_type_manager
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if not _service_type_manager:
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_service_type_manager = ServiceTypes(*args, **kwargs)
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return _service_type_manager
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@ -0,0 +1,38 @@
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# -*- coding: utf-8 -*-
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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test_singleton
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------------
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Tests for `get_service_types` singleton factory function.
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"""
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import os_service_types
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from os_service_types.tests import base
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class TestSingleton(base.TestCase):
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def setUp(self):
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super(TestSingleton, self).setUp()
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# Make an object with no network access
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self.service_types = os_service_types.get_service_types()
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def test_singleton_same(self):
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service_types = os_service_types.get_service_types()
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self.assertTrue(service_types is self.service_types)
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def test_singleton_different(self):
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service_types = os_service_types.ServiceTypes()
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self.assertFalse(service_types is self.service_types)
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@ -0,0 +1,7 @@
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---
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features:
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- |
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Factory function ``os_service_types.get_service_types`` added. Returns
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a singleton instance of ServiceTypes. ServiceTypes is a very low cost
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object in the first place, but it does read a data file from disk and
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then the data is pretty static.
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