SabreAPI | Python bindings to the Sabre REST API | REST library

I have made a component - let's call it CUSTOMSELECT, which takes a few inputs, e.g. the list of options for the dropdown, the default-selected option, a label and so on.

I want to use this component multiple times on some pages. For instance, I need a CUSTOMSELECT of employees, and within a nested component on the page, I need a CUSTOMSELECT of departments and another of roles.

OK, all fine so far. Each instance is correctly displayed with the desired data.

Now I want to publish any change of selection within an instance of a CUSTOMSELECT, so that I can so that I can subscribe to it. For instance, when an employee is selected, I want to refresh the rest of the page.

I created a service for this purpose. I linked the click event in the CUSTOMSELECT to a function which publishes the selected value to the service. In the parent component I have subscribed to the 'subject' so that I can action the change of employee.

That works.

But, if I then change the selection with the nested component's department CUSTOMSELECT, this value is published and the parent component's employee subscriber picks up the change and processes it. Not what I want to happen. Not at all!

So, how can I tell the observers to pay attention only to messages of interest to them? ie, how can I publish to the appropriate observer: the employee instance does not need to know that the department instance has changed value, and so on.

Thanks for any help - a whole day trying to figure this one out so far.

It may help to see the component tree like this: