Return list of table extensions using TableUtils() utility

[Sai Kumar B]

I always wonder, Is there any simple utility in ServiceNow to fetch the list of hierarchy/table extensions? 🤔

Well, By OOB we have TableUtils(). It contains multiple functions to perform on a table.

I will walk you through a few interesting functions.

getTables()  :  Returns list of table names in the table parent hierarchy

var hierarchyList = new TableUtils('cmdb_ci_server').getTables();
gs.print(hierarchyList); //Displays all its parent hierarchy along with the input

getTableExtensions() :  Returns list of table extensions

var hierarchyList = new TableUtils('cmdb_ci_server').getTableExtensions();
gs.print(hierarchyList); //Displays all its extensions

getAllExtensions()  : Returns list of table extensions including base table 

var hierarchyList = new TableUtils('cmdb_ci_server').getAllExtensions();
gs.print(hierarchyList); //Displays all its extensions including base 

Now, Let's iterate over the output. The output was displayed as an array list however, it's not an array 😐

It's an object and we have to convert it into an array as below 

var hierarchyList = new TableUtils('cmdb_ci_server').getTables();
gs.print(hierarchyList);

var arr = hierarchyList.toArray(); //Convert the output into an array 
for(var i=0; i<arr.length; i++){ //Iteration
    gs.print(arr[i]);
}

I hope you like my article 😊

Kindly, Post comments if any corrections are required 

Regards,
Sai Kumar

[Sohail Khilji]

good one !

[David Casper]

Great post, first found this a long time ago. 

However, I just had to reuse the getTableExtensions method and noticed some interesting things. 

1) When using the getTableExtensions method, I had to use .size() rather than .length in order to read the elements within the array. Any ideas why? Assuming the type of array it's creating and I don't remember having to do this before. 

2) When looking at a specific element in the array I'm unable to use array[i] I have to use array.get(i)

Really would like to understand what's going on behind the scenes here so I know why this was required. Looks like this might be creating a Java array? Thanks!

[jacobperry-]

@David Casper

1) When using the getTableExtensions method, I had to use .size() rather than .length in order to read the elements within the array. Any ideas why? Assuming the type of array it's creating and I don't remember having to do this before.

2) When looking at a specific element in the array I'm unable to use array[i] I have to use array.get(i)

You are correct, it's returning a Java Object, specifically java.util.ArrayList. Whenever you encounter this behaviour, you can wrap the output in j2js() convert the Java Object into an equivalent Javascript object. 

new TableUtils('cmdb_ci_server').getTables() //Returns Java ArrayList
j2js(new TableUtils('cmdb_ci_server').getTables()) //Returns Javascript Array

If you look at the TableUtils script include, you will see these methods invoke the respective GlideDBObjectManager methods.