Field validation

in a before_save logic hook:

function before_save ($bean,$event,$arguments){

    $what_the_value_was = $bean->fetched_row['field_name']

    $what_the_value_is_now = $bean->field_name

    if($what_the_value_was != $what_the_value_is_now){

       //the value has changed.

    }

)

In the record view controller you can get a list of the changed fields with: 

Object.keys(this.model.changedAttributes(this.model.getSynced())); 

FrancescaS

Thank you soo much Francesca Shiekh  you've helped me a lot.