Validate Record Data

This trigger validates the record's data using an expression. If the expression results in an error (i.e. a non-null value expected as a string message), the data operation is terminated and an error message is displayed. This is similar to the situation where a field validation fails when creating or modifying a record. To use this trigger, provide a formula expression to validate. The formula returns a string error message when validation fails. It returns an empty string or null if the validation succeeds. For example:

if ({!amount} > 100000) 
   return "Order is too large: {!amount}";
   else
   return null;

Another example:

if ("{!email}" == ""  && "{!phone}" == "") 
   return "Either email or phone must be specified";
   else
   return null;