Replace cached method calls with @memoized_method

[Radomir Dopieralski]

There is a certain pattern repeated all over openstack_dashboard for caching results of method calls. It looks something like this:

    def get_data(self):
        if not hasattr(self, "_data"):
            # Calculate data here.
            self._data = data
        return self._data

This repeating pattern is an example of copy-and-paste programming and can be instead easily abstracted away into a decorator. This way all the logic is in one place and all the code benefits from bugfixes and performance improvement of that code.

[Ladislav Smola (lsmola)]

Yeah, this one is ugly. Thanks for picking this up.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/54094
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=b7537a8b8155fcf112067eb7d9d12339e280e44f
Submitter: Jenkins
Branch: master

commit b7537a8b8155fcf112067eb7d9d12339e280e44f
Author: Radomir Dopieralski <email address hidden>
Date: Mon Oct 28 11:24:00 2013 +0100

    Use memoized_method decorator in views

    A lot of horizon's views use the pattern:

        def get_data(self):
            if not hasattr(self, "_data"):
                # Calculate data here.
                self._data = data
            return self._data

    This is copy-pasted all over the codebase. It's better to handle that
    with a single decorator. In the future, we might even replace it with
    some better caching approach.

    Closes-bug: #1248230
    Change-Id: Id021fccf9032e5068993ec91a7774a5d0fbf29bb