opal.core.discoverable

The opal.core.discoverable module contans base discoverable classes for creating features which can be re-used and subcalssd.

DiscoverableFeature

The base discoverable class which provides functionality to all discoverables.

DiscoverableFeature properties

DiscoverableFeature.module_name

The name of the python module in which Opal will look for instances of this discoverable. For instance in the following feature, Opal would look in every installed app at app/ciao.py for subclasses of Greeting, even if that module had not been directly imported already.

from opal.core import discoverable

class Greeting(discoverable.DiscoverableFeature):
  module_name = 'ciao'

DiscoverableFeature.display_name

The human readable name for an instance of a discoverable. Use this in the UI when showing the discoverable to users.

DiscoverableFeature.slug

The slug for this discoverable used in URLs. Note that Opal internally useses the get_slug method below to allow more dynamic slugs.

DiscoverableFeature classmethods

DiscoverableFeature.is_valid()

Stub function that is called at class definition to determine whether an instance is valid. Useful for enforcing business logic and expectations for third party features. Expected to raise an exception if something is wrong.

DiscoverableFeature.get_slug()

Return the slug for this feature. Defaults to returning the slug property if it is set, or running a slugify function on the display_name. If neither is set it will raise a ValueError.

MyFeature.get_slug()
# -> "my-feature"

DiscoverableFeature.list()

Return a generator that yields all implementations of a discoverable.

for g in Greeting.list():
    print g.display_name

"Bonjour"
"Hola"
"Namaste"
"Salaam"

DiscoverableFeature.filter(**kwargs)

Find instances of a feature based on the value of their attributes. You may pass attributes of features as keyword arguments. Returns a list of matching features.

Greeting.filter(module_name='ciao') # Essentially the same as .list()

Greeting.filter(slug="bonjour", display_name="Bonjour")
# -> [BonjourGreeting]

SortableFeature

A mixin class that provides ordering for features which will be respected by both list() and filter().

Properties

SortableFeature.order

An integer which is used to sort features.

SortableFeature classmethods

SortableFeature.list()

Returns instances of the feature orderd by .order

class Greeting(discoverable.DiscoverableFeature,
               discoverable.SortableFeature):
    module_name='ciao'

class Namaste(Greeting):
    order = 2

class Hello(Greeting):
    order = 32098239021

class Bonjour(Greeting):
    order = 1

for f in Greeting.list():
    print f, f.order

# <class '*.*.Bonjour'>, 1
# <class '*.*.Namaste'>, 2
# <class '*.*.Hello'>, 3

RestrictableFeature

A mixin class that provides an interface for restricting access to features based on user.

class Greeting(discoverable.DiscoverableFeature,
               discoverable.RestrictableFeature):
    module_name='ciao'

RestrictableFeature classmethods

RestrictableFeature.for_user(user)

Generator method that yields all instances of this discoverable which are visible to a given user.

for f in Greeting.for_user(user):
    print f

# <class '*.*.Bonjour'>
# <class '*.*.Namaste'>
# <class '*.*.Hello'>

RestrictableFeature.visible_to(user)

Predicate function used to determine whehter in individual feature should be visible to a given user. Defaults to simply returning True.

Features may override this to provide restricted access as required.

Hello.visible_to(user) # -> True

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