envisage.i_service_registry module

The service registry interface.

class envisage.i_service_registry.IServiceRegistry(adaptee, default=<class 'traits.adaptation.adaptation_error.AdaptationError'>)

Bases: Interface

The service registry interface.

The service registry provides a ‘Yellow Pages’ style mechanism, in that services are published and looked up by protocol (meaning, interface, type, or class (for old-style classes!). It is called a ‘Yellow Pages’ mechanism because it is just like looking up a telephone number in the ‘Yellow Pages’ phone book. You use the ‘Yellow Pages’ instead of the ‘White Pages’ when you don’t know the name of the person you want to call but you do know what kind of service you require. For example, if you have a leaking pipe, you know you need a plumber, so you pick up your ‘Yellow Pages’, go to the ‘Plumbers’ section and choose one that seems to fit the bill based on price, location, certification, etc. The service registry does exactly the same thing as the ‘Yellow Pages’, only with objects, and it even allows you to publish your own entries for free (unlike the real one)!

get_service(protocol, query='', minimize='', maximize='')

Return at most one service that matches the specified query.

The protocol can be an actual class or interface, or the name of a class or interface in the form ‘<module_name>.<class_name>’.

Return None if no such service is found.

If no query is specified then a service that provides the specified protocol is returned (if one exists).

NOTE: If more than one service exists that match the criteria then Don’t try to guess which one it will return - it is random!

get_service_from_id(service_id)

Return the service with the specified id.

If no such service exists a ‘ValueError’ exception is raised.

get_service_properties(service_id)

Return the dictionary of properties associated with a service.

If no such service exists a ‘ValueError’ exception is raised.

The properties returned are ‘live’ i.e. changing them immediately changes the service registration.

get_services(protocol, query='', minimize='', maximize='')

Return all services that match the specified query.

The protocol can be an actual class or interface, or the name of a class or interface in the form ‘<module_name>.<class_name>’.

If no services match the query, then an empty list is returned.

If no query is specified then all services that provide the specified protocol are returned (if any exist).

register_service(protocol, obj, properties=None)

Register a service.

The protocol can be an actual class or interface, or the name of a class or interface in the form:

'foo.bar.baz'

Which is turned into the equivalent of an import statement that looks like:

from foo.bar import baz

Return a service Id that can be used to unregister the service and to get/set any service properties.

If ‘obj’ does not implement the specified protocol then it is treated as a ‘service factory’ that will be called the first time a service of the appropriate type is requested. A ‘service factory’ is simply a callable that takes the properties specified here as keyword arguments and returns an object. For really lazy loading, the factory can also be specified as a string which is used to import the callable.

set_service_properties(service_id, properties)

Set the dictionary of properties associated with a service.

If no such service exists a ‘ValueError’ exception is raised.

unregister_service(service_id)

Unregister a service.

If no such service exists a ‘ValueError’ exception is raised.