Type coercion in FileMaker: GetAsNumber, GetAsText, GetAsDate

Beginner

FileMaker fields have types, but calculations sometimes return the wrong type for the context. Learn how GetAsNumber, GetAsText, and GetAsDate coerce values and why type mismatches cause silent bugs.

What you'll learn

When and why implicit coercion fails silently in FileMaker
How GetAsNumber, GetAsText, and GetAsDate force the correct type
The pattern for checking whether a value is a valid number

FileMaker performs implicit type coercion in some contexts and not others — using GetAsNumber, GetAsText, and GetAsDate explicitly ensures your calculations behave predictably regardless of field type.

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Convert text to a number for arithmetic

If a value comes from a text field or a JSON parse, wrap it in GetAsNumber before arithmetic. Text that cannot be converted returns 0, not an error.

FileMaker Script

# $quantity comes from a JSON parameter — it may be a string
Set Variable [ $qty   ; Value: GetAsNumber ( JSONGetElement ( $param ; "quantity" ) ) ]
Set Variable [ $price ; Value: GetAsNumber ( JSONGetElement ( $param ; "price" ) ) ]

# Safe arithmetic — both values are confirmed numbers
Set Variable [ $total ; Value: $qty * $price ]

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