Validators

The Global Variable Validator is a global server configuration property which allows validation rules to be defined for any number of specific variables.

This property defines a list of variables to be validated.

Property Name: validator

Property type: Data Table

Each record in this table defines a variable to be validated:

• Variable. The exact variable name to be validated. If a variable with this name does not exist in any context matching the context mask, the validator will not execute the expression.
• Context Mask. The context or contexts in which the validator should be listen for the variable being set.
• Validator expression. Expression which returns 'NULL' for a valid variable value or ‘string’ to be used as exception text for invalid values

The validator listens for set operations acting on variables which match the indicated variable name in a context which matches the indicated context mask.

The expression is executed before the variable is set. If the output of the expression is ‘null’ then the variable will be set with the indicated value. If the expression output is a string, the variable is not set, an exception is thrown, and the provided string is used as the exception message.

This will allow the 'syncRate' variable in all devices to take values greater than 100, and in all other cases throw and exception with the indicated text.

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