Module development and code questions

I am working from this tutorial and I want to load a node entity in a Controller class.

The following construct (copied almost verbatim):

$entity = \Drupal::entityTypeManager()->getStorage('node')->load(1);

works as expected.

The same tutorial says:

Hi,

I have a module with a bunch of entities : single_page and single_page_item. I use this module on several sites. When I created my module that declare these entities and use it, I didn't add the uuid value to it.

Now I would like to use it with linkit module and see that the entities MUST have uuid to be linked.

I ask myself how to add uuid to my entities and don't break my actual system. If anyone has some suggestions it would be very helpful because I'm not comfortable with adding new fields to entities after deployment...

Hi

I'm a bit of a veteran PHP developer and have maintained and kept my own CMS going for 20 years now.  (Originally written in perl!!!!)  I know the naysayers will tell me "just use something already out there" but it is a (sick) hobby of mine and I wish to integrate my CMS with a drupal base for security that Drupal provides. 

My employer went to Drupal 3 years ago.  My role in my career is to not only use it, but I am also an instructor to teach our department 'web champions' how to use the Drupal CMS we have.  So, I know the ins and outs of Drupal on the front end.

Hi,

I'm new at using Drupal, I'm trying to generate a table with different colored rows, based on a status variable, so I created a class based on that status.

This is part of my code:

I am working on some functionality that is 'similar' to the 'browse available tokens' functionality in Drupal core. I have a main form that has a link that opens a modal (with another form in it). Inside that additional form, users are able to search in that form, and each result comes with some data as well as a 'add to item' button. When the user clicks 'add to item', it closes the modal and updates the main form with the relevant information from the sub form (based on the unique results button they clicked on).

Note: I originally posted this in a different sub-forum, so I copied it here because it seems more relevant to module development than general post-installation support.