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      How to validate a form field for a barcode format like ABCD0312

      This guide shows how to create a validation rule that ensures: The first 4 characters are uppercase letters (A–Z) and the last 4 characters are digits (0–9)

      Scenario

      You have a field called "barcode" in your form, and you want to match it against this structure:

      AAAA0000
      ↑   ↑
      |   └── Four digits
      └────── Four capital letters

      For example, the following inputs should be considered valid:
      Input Valid?
      ABCD0312 ✅ Yes
      abcD0312 ❌ No
      ABCD123 ❌ No
      A1C20312 ❌ No
      ABCD03123 ❌ No
       
       
       
       
       
       

      Rule Configuration

      Step 1 - In the barcode field, navigate to the 'Field Validation Rules' tab

      Step 2 - "Mark form as Valid without message, when"

      data["Barcode"] =~ "^[A-Z]{4}[0-9]{4}$"

      This regex means:

      • ^[A-Z]{4} → Starts with 4 capital letters

      • [0-9]{4}$ → Ends with 4 digits

      • ^...$ → Anchors it to exactly 8 characters, no more, no less


      Step 3 -       Add a new validation rule with the '+' icon

      Step 4 - Click the 'valid' button to change to 'Invalid' and select a colour

      Step 5 - "Otherwise, mark form as Invalid without message, when"1

      1==1

      This always evaluates as true, meaning any unmatched input is invalid by default.