Navigation:  Commands > Infobox Information File [IIF] > $set_chain [IIF]

Establish a Chain of Infobox Sequences

$set_chain [nextboxspec[,nextboxspec...]]

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This command establishes a chain of infobox sequences or actions.  Each standalone infobox, or sequence of infoboxes, must end with a $chain command to transfer control to the next element in the chain. However the standalone infobox, or sequences of infoboxes can also be used independently, with the $chain command transferring control to a designated place in the absence of a chain, or when the end of the chain is reached. This ability to use the infoboxes independently gives the chain feature an advantage over manually creating a 'hard-wired' chain with a series of $next_box commands.

The parameter on this command normally consists of a sequence of infobox names:

Processing of the chain commences with a $chain command which should follow the $set_chain.

As each standalone infobox or infobox sequence ending with a $chain command is reached, control transfers to the next item in the chain.  At the end of the chain, control transfers by default to state 191 (IIF_PROC_COMPLETE). You can override this by assigning an infobox name, state name or state number to system variable CHAIN_END.

A $set_chain command with no parameters clears any established chain and causes control to transfer from the next $chain command to state 191 or the defined CHAIN_END.  If you are using a chain, and you transfer out to a completely separate sequence of infoboxes, for example on an $error_exit command, it is usually a good idea to clear the chain with a $set_chain command having no parameters. This does not happen automatically. Although similar to the existing $set_state feature, the chain operates independently of any state traps.

The chain and chain end exist until the end of the call or the pre- or post-process or until overridden by a later definition. The NEXT_CHAIN and FULL_CHAIN system variables return the next chain destination and the remainder of the unprocessed chain, respectively. The parameter on the $set_chain command can be specified as a variable expansion, which makes it easier to select different combinations of infoboxes.  See the examples below.

Examples:

Set a simple list of infoboxes to be processed in turn. This example starts infobox ActionA and processes infoboxes until one with a $chain command is reached, when control is passed to infobox ActionD, and so on to ActionK. After starting infobox ActionK, the next $chain command will transfer to state 191.

;POSTPROC.IIF

$set_chain ActionA,ActionD,ActionK

$chain   ; start from ActionA

Select from multiple pre-defined chains:

;POSTPROC.IIF

$set_var CHAIN1 ActionA,ActionC

$set_var CHAIN2 ActionA,ActionB,ActionC

$if @varname = 1

  $set_chain @CHAIN1

$else

  $set_chain @CHAIN2

$chain

Use the system variable NEXT_CHAIN to determine the next destination:

;ACTIONA.IIF

$type decision

$if @NEXT_CHAIN = ACTIONB

  $set_var ROUTE B_NEXT

$endif

$chain

Use the system variable FULL_CHAIN to get the whole of the remaining chain, and insert an additional step at the end:

;ACTIONA.IIF

$type decsion

$if @varname > 7

  $set_var WORK @FULL_CHAIN

  $set_var WORK |,ActionK

  $set_chain @WORK

$endif

$chain

In an IVR application, end the chain other than at state 191:

$type decision

$set_var CHAIN_END s:HANG_UP

$set_chain ActionA,ActionB

$chain

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