Perform Script with parameter: JSON encoding and decoding

Beginner

Pass structured data between scripts by encoding parameters as JSON objects and decoding them with JSONGetElement in the receiving script.

What you'll learn

How to encode multiple values into a JSON script parameter
How to decode the parameter in the receiving script with JSONGetElement
How to define a consistent parameter contract for reusable scripts
How to handle missing or malformed parameters defensively
How to pass a JSON parameter through multiple levels of script calls

FileMaker's Perform Script step accepts a single text string as a parameter. By encoding that string as a JSON object you can pass multiple named values in one call, making sub-scripts self-documenting and eliminating the need for $$global variables as a handoff mechanism. The receiving script decodes the parameter with JSONGetElement at the start.

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Build a JSON parameter before calling Perform Script

Use JSONSetElement to build the parameter object in the caller. Name keys descriptively -- the sub-script's developer reads these names to understand what to expect. Pass the variable directly into the Parameter field of Perform Script.

FileMaker Script

# Caller script
Set Variable [ $params ; Value:
  JSONSetElement ( "{}" ;
    [ "clientID" ; Clients::ClientID ; JSONString ] ;
    [ "invoiceDate" ; Get ( CurrentDate ) ; JSONString ] ;
    [ "sendEmail" ; 1 ; JSONBoolean ] ;
    [ "calledBy" ; Get ( ScriptName ) ; JSONString ]
  )
]
Perform Script [ "Create Invoice" ; Parameter: $params ]
Set Variable [ $result ; Value: Get ( ScriptResult ) ]

Script continuation and halt: Halt Script, Exit Script, and Allow User Abort Commit Records: skip validation and no-dialog flags