Error recovery patterns: the FileMaker Try-Catch equivalent

Expert

Implement structured error recovery in FileMaker scripts using OnError labels, error translation tables, and cleanup routines that mirror try-catch patterns.

What you'll learn

How to implement the try-catch pattern with OnError labels
How to build an error translation table for common FileMaker error codes
How to implement a finally block equivalent for cleanup that always runs
How to propagate errors through multiple levels of script calls
How to distinguish retryable errors from fatal ones

FileMaker has no native try-catch syntax, but the combination of OnError [ Go to [label] ], Set Error Capture [ On ], and a cleanup label creates an equivalent pattern. When implemented consistently, this gives every script a predictable error surface: errors jump to a known handler, get translated into human-readable messages, trigger cleanup, and exit with a structured result the caller can inspect.

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The standard try-catch script skeleton

Every script that touches data should follow this skeleton: Set Error Capture On, OnError to the error label, main logic, Exit Script with success, then an error label that captures the code, translates it, runs cleanup, and exits with a failure result.

FileMaker Script

# Script: Invoice - Commit
Set Error Capture [ On ]
OnError [ Go to [::HandleError] ]

# -- TRY BLOCK ------------------------------
Commit Records/Requests [ Skip data entry validation: Off ; No dialog: On ]
# If this step fails, FileMaker jumps to ::HandleError

Exit Script [ Text Result:
  JSONSetElement ( "{}" ; [ "success" ; True ; JSONBoolean ] )
]

# -- CATCH BLOCK ----------------------------
::HandleError
Set Variable [ $code ; Value: Get ( LastError ) ]
Set Variable [ $message ; Value:
  Case (
    $code = 301 ; "This record is locked by another user. Please try again in a moment." ;
    $code = 500 ; "A required field is empty. Please complete all required fields." ;
    $code = 301 ; "Record is currently in use." ;
    "An unexpected error occurred (code " & $code & ")."
  )
]
# -- FINALLY BLOCK (cleanup) ----------------
Allow User Abort [ On ]
# -- EXIT WITH ERROR ------------------------
Exit Script [ Text Result:
  JSONSetElement ( "{}" ;
    [ "success" ; False ; JSONBoolean ] ;
    [ "error" ; $message ; JSONString ] ;
    [ "code" ; $code ; JSONNumber ]
  )
]

Script design patterns: single responsibility and naming Modular script libraries in FileMaker