registerDomain
registerDomain — registers to receive updates from domain
points.
Syntax
For C++:
ST_STATUS registerDomain( | LPCTSTR | domainname, |
| | int | flags); |
For Java and C#:
Exception registerDomain( | String | domainname, |
| | int | flags); |
Parameters
- domainname
- The name of a domain.
- flags
Specifies conditions and actions associated
with registering the domain points, as
follows (flags may be combined):
- DHC_FLAG_REG_FUTURE:
points created in the future are also affected. If
not set, then only those points existing (in the
domain) at the time the command message is
received by the DataHub are registered.
- DHC_FLAG_REG_QUALIFY:
point names are to be transmitted with the domain
name prepended to the point name, as
domainname:pointname.
- DHC_FLAG_REG_ONCEONLY:
the point values are transmitted only once, and
the points remain unregistered. This mode is
useful for obtaining an initial list of available
points from which a selection is made of which
ones to register.
Returns
For C++:
- ST_OK if the command was
successfully sent to the DataHub. Since the command
is sent asynchronously, the actual success or failure
of the command must be determined through the onSuccess
or onError
message handlers.
- ST_NO_TASK if a connection to
the DataHub does not exist.
- ST_ERROR if the connection
socket is unable to send the message.
Description
This method registers the client
to receive updates from the DataHub when the value of any
points in the specified domain change. The onPointChange method is called for
each point update received. The
registerDomain method may be called more
than once, and on different domains.
Upon registering
the domain, all points currently in that domain of the DataHub
are immediately transmitted to the client. Points that are subsequently
created will only be sent if the
DHC_FLAG_REG_FUTURE flag is specified. The
DHC_FLAG_REG_QUALIFY flag is useful for
distinguishing points from different domains that have the same
name.
In a typical scenario, either there is no need
to register for all points, or the point names are not even known.
In either case, you can use the
DHC_FLAG_REG_ONCEONLY flag to generate an
initial list of all available points in the specified domain. Then
you can call registerPoint on any points of
interest, as they are received in onPointChange.
