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As you're just discussing inside of our order created listener right after we save our ticket we're

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going to want to publish an event saying that this ticket was just updated that is going to allow our

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different replicated services or services that have replicated data to stay in sync now to put this

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update together.

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I first want to give you a quick reminder on how we publish an event in general as we had spent a little

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bit of time since we have published an event inside of our ticket service.

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You might recall that we have a publishers directory inside there is the ticket updated publisher.

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So this is the classic we used to publish an event saying that a ticket has been updated to make use

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of this.

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We create an instance of the publisher we pass in a Nats client.

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So that might be something like Nats report clients and we'll call the publish function and is publish

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function is going to have all the properties that are going to be contained inside the event.

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Now unfortunately our ticket updated event definition is just a little bit out of date.

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In particular you'll notice that we are saying that this event is going to have an I.D. a version title

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price and user I.D. but our ticket also now has an order I.D. property tied to it as well this event

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object right here does not yet support that order.

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I.D. property chances are that whenever we update a ticket we're going to want to tell every other service

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whether or not this ticket is reserved.

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And we would do that by sharing that order I.D. property.

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So we should probably go back over to our common module very quickly and make sure that we add in to

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this event definition or the definition for ticket updated.

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You say that the event is going to have an order I.D. property as well.

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But before we do so there's one other very quick thing I want to mention I'm going to go back over to

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the order created listener at the top.

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I'm going to import the publisher that we're just taking a look at that we'll get the ticket updated.

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Publisher from up one directory publishers ticket update publisher and then very quickly I want to imagine

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how we're going to write this out right after that ticket not safe.

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Well just as we saw on that other file we would probably write out something that looks like new ticket

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updated publisher and then we would want to pass in our Nats client right here.

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Now there are two different ways that we can provide a Nats client.

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One is going to be very easy and direct the others can be a little bit harder to understand but ultimately

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a lot easier.

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So in order to provide a Nats client right here the easy solution that will work right away without

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any changes would be to import our Nats rapper from up to directories Nats rapper and then we could

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provide that to the publisher

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like so easy enough.

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No problem whatsoever.

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Right.

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Well there is a downside to this approach.

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The downside is that we are adding in yet another tie between two different files inside of our projects.

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So we are importing the Nats wrapper directly into order created listener.

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Normally that is unavoidable at some point time.

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We just have to tie different files together.

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And that's life.

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That's just how stuff works.

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However because you have already seen that testing a lot of these listeners revolves around somehow

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mocking this Nats rapper right here.

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If we had in a direct report for NATS rapper that might make testing a little bit more challenging down

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the line.

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So it turns out that there actually is a slightly easier way to approach this.

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It is just going to involve making one other very quick change inside of our common module.

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So let's take a look at a quick diagram and understand what the other option is.

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OK so this is what we are doing right now.

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We've got our order created listener.

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It is trying to create an instance of ticket updated publisher and we are doing so by importing the

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Nats rapper into the order created a listener.

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We're going to take that things client and then pass it off to the ticket.

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Updated publisher but there's something else I want you to recall the order created listener is a subclass

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of the listener base class.

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Let's go take a look at that listener base class definition.

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Very quickly we're going to see something really interesting our listener base class is defined inside

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of our common module so I'll go to my common module s our RC events and then find base listener T.S.

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inside of here.

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You might recall that whenever we create an instance of a listener or anything that extends a listener

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for that matter we are required to provide a Nats client.

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That's what this constructor function is saying right here.

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We then assign that to the distant client property and we had marked this stock client or the client

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property as private which means that it cannot be accessed by any other class even a subclass so technically

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our order created listener.

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That is what we are working on right now.

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It is a subclass or a child class of the listener.

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So inside of order create a listener they're technically already is a Nats client kind of wrapped up

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into this thing but unfortunately we had marked it as a private property which means that this child

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class cannot access that client property diagram format.

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This is what it looks like we've got our ordinary listener.

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It is extending the listener listener definitely already has a initialized Nats client is there ready

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to be taken.

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So if we could somehow get a handle on that thing we could very easily pass it through to the ticket

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update a publisher without having to worry about that Nats wrapper class or anything like that.

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The only reason we cannot do this right now is because we had marked that client property as private

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and again if a client or to if a property is marked as private we can not access it from anywhere outside

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the class even in a child class.

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So to fix this inside of our common module we could just update the modifier on that property.

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We could instead market as protected if we market as protected.

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That means that the child class of ordinary listener can access that property it can access the client

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take the client and pass it off to the ticket.

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Updated publisher and so this would be a way preferable solution because it's gonna make testing easier

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down the line.

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And it's also going to mean that we've got one less direct tie between two different files inside of

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a project which again is usually a pretty good thing.

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OK.

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So at this point what we've really established inside of this video is that we really need to go over

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to our common module and make two changes.

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The first change we need to make is a change to our ticket updated events.

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We need to make sure that the ticket update event also communicates an order ideas property and then

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we've also established that our base listener.

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We need to mark that client as a protected property instead of private now that we've established what

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we have to do.

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Quick pause right here.

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Make those two changes in the next video.