Why does GlideRecord.getValue('field_name') return null for blank columns?

[wfurman]

//Using Eureka version - Background Scripts

var grContact = new GlideRecord('u_staging_ess_contacts');
if (grContact.get('u_first_name', 'Rachel')) {
  gs.print(grContact.getValue('u_mobile_phone'));   //returns null   (initially a blank string if viewed with the form)
  gs.print(grContact.getValue('u_home_phone'));   //returns a value XXX-XXX-XXX   (a non-blank value when viewed with the form)
  grContact.setValue('u_home_phone', grContact.getValue('u_mobile_phone'));
  grContact.update();
  gs.print(grContact.getValue('u_mobile_phone'));   //returns null
  gs.print(grContact.getValue('u_home_phone'));   //returns null   (but no update was actually made to the record)
}

//Then run this right after.....

var grContact = new GlideRecord('u_staging_ess_contacts');

if (grContact.get('u_first_name', 'Rachel')) {

  gs.print(grContact.getValue('u_mobile_phone'));   //returns null

  gs.print(grContact.getValue('u_home_phone'));   //returns original value XXX-XXX-XXX, field was not updated

}

/* Questions
u_home_phone is not updated, since it appears that setValue('u_home_phone', null) silently fails.
Why does grContact.getValue('u_mobile_phone') return a JavaScript null and not ''?   I started relying on setValue and getValue on the GlideRecord based on listening to a TechNow Server-Side Scripting video, but am beginning to doubt the validity of their use in all cases.

I switched to using grContact.u_mobile_phone.getDisplayValue(), but it would be nice to be consistent with getValue and setValue.   I don't want to have
to test the return value for null.   I need an easy API to move values between a normal table and a staging table for export where I don't have to worry about the type.

While I am at it - Why isn't the call GlideRecord.getDisplayValue('my_field_name') documented in GlideRecord.   It only documents returning the DisplayValue
for the record and not the specified field?   Is the documentation off?

*/

[Slava Savitsky]

Perhaps using getElement() or getElementValue() could help in this case.

GlideElement - ServiceNow Wiki

https://developer.servicenow.com/app.do#!/api_doc?to=method_class__getelement_string_columnname__gli...

[wfurman]

I think there is a bug,   I am using a workaround that requires testing the value before sending it into setValue.   An enhancement request was submitted on my behalf.

[andrewkinca · Accepted solution]

Hi Wright!   I'm sorry that our TechNow video led you to a more frustrating experience.   If it makes you feel any better, I also do not like that getValue() returns null for an empty field (and for a non-existent field.)   While I cannot say why it is this way, it has been this way for a long time.   I can tell you what I typically do, although it is more code.

I either OR the getValue call with an empty string like:

var x = gr.getValue('something') || '';

Or, I use a custom getValueAK function that also supports dot-walking.   I usually include this function in the script itself, or I dump this into a Script Include:

// You can put this in a Script Include
// Features:
// - always returns a string
// - can dot-walk
// - returns empty string instead of null (for both empty fields and non-existent fields)
// - returns string 'true' or string 'false' for boolean fields
function getValueAK(field, ge) {

       // Local vars
       var fields;

       // If you don't pass in anything, you get an empty string
       if (!field) {
               return '';
       }

       // If no second parameter, assume this
       if (!ge) {
               ge = this;
       }

       // Split fields on dot
       fields = field.split('.');

       // If there is only one field
       if (fields.length === 1) {

               // If the field exists, return a string, else return empty string
               return ge[field] !== undefined ? String(ge[field]) : '';

       } else {

               // If there is more than one field, recurse
               return this.getValueAK(fields.slice(1).join("."), ge[fields.slice(0, 1)]);
       }

}

And you can use it like this:

var gr = new GlideRecord('incident');
gr.getValueAK = getValueAK;
gr.get('d71f7935c0a8016700802b64c67c11c6');
gs.print(gr.getValueAK('caller_id.manager.name'));

I hope this helps!

[kikhtenko]

Good solution,

I would make this script easier to get rid of recursion... something like this:

function getValueAK(name, gr) {

  var names = name.split('.');

  var obj = gr;

  for (var i = 0; i < names.length; i++) {

      var field = names[i];

      obj = obj[field];

      if (gs.nil(obj)) {

          obj = null;

          break;

      }

  }

  return obj ? obj.toString() : '';

}

Regards,

Andrii