How to create an expression rule in which pass another exp rule as rule input

Question

Hi, 
 
 Requirement is to create one expression rule in which I need to pass another expression rule as rule input, 
 
 I do not know what type of rule input to define. 
 
 Use Case - Have integration, need to call through expression rules, if integration is failed, I need to retry n number of time. and if it returns success, break the calling chain of integration 
 
 Thanks, in advance. 
 Shree Krishna

Mike Schmitt · Answer

I'm not really clear what you're asking. 
 In an expression rule you can, trivially easily, call another expression rule within it, either to populate a local variable, or to define the output (or some part of the output). Likewise, any parent objects that call an expression rule, can call a different expression rule as part of the top-level expression rule call's rule inputs, presuming that the "lower" rule returns an output that will be compatible with the data type of the rule input it's being assigned into.

Mike Schmitt · Answer

The best way to do this is to build a process model where the integration is called directly from the appropriate smart service node , and if it fails, handle it with a process loop (increment a counter and have the loop give up after a certain number). You can even add a 5 or 10 second timer in between each try. 
 I expect the approach you're trying in which you do it all within some complex nested expression structure is going to result only in frustration on your end.

Mathieu Drouin · Answer

There are ways to call expression rules dynamically but really doubt it applies to your use case. I think Mike's suggestion is your best bet.