#2. One-to-Many (1:N) Relationships
This is a real example which illustrates a one-to-many relationship between one Location and many Devices.
From Device.py
... from Products.ZenRelations.RelSchema import * ... class Device(ManagedEntity, Commandable): ... event_key= portal_type = meta_type = 'Device' default_catalog= "deviceSearch" #device ZCatalog relationshipManagerPathRestriction = '/Devices' ... _relations = ManagedEntity._relations + ( ("location", ToOne(ToMany, "Location", "devices")), ) ...From Location.py
... from Products.ZenRelations.RelSchema import * #
... class Location(DeviceOrganizer): ... # Organizer configuration dmdRootName = "Locations" portal_type = meta_type = event_key = 'Location' _relations#
= DeviceOrganizer._relations + ( ("devices" #
, ToMany(ToOne,"Device","location")),#
) ...According to this relationship there can be only one Location assigned to a Device but more than one Device assigned to a Location. This relationship is created by:
| Importing ToOne and ToMany from Products.ZenRelations.RelSchema. |
| Appending a two-item tuple to the _relations attribute |
| The first item in the tuple is a "string" object which is the local name |
| The second item in the tuple is a RelSchema constructors takes three parameters:
|
