Notifications

Use the following methods to subscribe to a notification, publish a notification with specified data, and unsubscribe from a notification. This allows scripts running within the same Core to communicate with each other using control wiring or Component.

Methods

Name

Attribute/Arguments

Comment

noteid = Notifications.Subscribe()

name, function

Subscribe to a notification with a given name.

  • noteid: The token to use when unsubscribing from a notification.
  • name: The name of the notification.
  • function: The callback to call when the named notification is triggered. The signature is function( name, data ).

Notifications.Publish()

name, data

Publish a named notification with given data. The data can be either a Lua table or a string.

Note: You cannot call the Notifications.Publish() method inside a Notifications.Subscribe() callback. This will raise a Lua error.

Notifications.Unsubscribe()

noteid

Unsubscribe from a notification with the specified noteid.

In this example, two Scriptable Controls components are configured - Thing 1 and Thing 2. Control wiring connects exposed Code control pins. Thing 1 is subscribed to receive notifications from Thing 2 and vice versa. When the Send button is pushed on one component, the other receives the Send String text and the Received LED illuminates. If the Unsubscribe button is pushed, notifications are no longer received from the other component.

See the table below for the complete Lua code example from each Scriptable Controls component. All Notifications methods are used in this example.

Note: In Q-SYS Designer version 7.2 and higher, the Text Controller component replaces Scriptable Controls.

Thing 1 Thing 2
Copy 
send = Controls.Send
txstr = Controls["Send String"]
txid = Controls["Notify ID"]
rxled = Controls.Received
rxstr = Controls["Receive String"]
rxid = Controls["Receive ID"]
sub = Controls.Subscribed
unsub = Controls.Unsubscribe

local noteid

function RXHandler(name,data)
  print(string.format("Notification Name: \"%s\"\t Data: \"%s\"",name,data))
  rxstr.String = data
  rxled.Boolean = true
  Timer.CallAfter(function() rxled.Boolean = false end, 1)
end

function Subscribe()
  local id = rxid.String
  if #id>0 then
    noteid = Notifications.Subscribe( id, RXHandler )
    if noteid then
      sub.Boolean = true
    end
  end
end
rxid.EventHandler = Subscribe
Subscribe()

send.EventHandler = function()
  local tx = txstr.String
  if #tx>0 and #txid.String>0 then
    Notifications.Publish( txid.String, tx )
  end
end

unsub.EventHandler = function()
  if noteid~=nil then
    Notifications.Unsubscribe(noteid)
    sub.Boolean = false
    rxstr.String = ""
    rxid.String = ""
  end
end
Copy 
send = Controls.Send
txstr = Controls["Send String"]
txid = Controls["Notify ID"]
rxled = Controls.Received
rxstr = Controls["Receive String"]
rxid = Controls["Receive ID"]
sub = Controls.Subscribed
unsub = Controls.Unsubscribe

local noteid

function RXHandler(name,data)
  print(string.format("Notification Name: \"%s\"\t Data: \"%s\"",name,data))
  rxstr.String = data
  rxled.Boolean = true
  Timer.CallAfter(function() rxled.Boolean = false end, 1)
end

function Subscribe()
  local id = rxid.String
  if #id>0 then
    noteid = Notifications.Subscribe( id, RXHandler )
    if noteid then
      sub.Boolean = true
    end
  end
end
rxid.EventHandler = Subscribe
Subscribe()

send.EventHandler = function()
  local tx = txstr.String
  if #tx>0 and #txid.String>0 then
    Notifications.Publish( txid.String, tx )
  end
end

unsub.EventHandler = function()
  if noteid~=nil then
    Notifications.Unsubscribe(noteid)
    sub.Boolean = false
    rxstr.String = ""
    rxid.String = ""
  end
end