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Now that we've got that subjects in on put together we're going to put together a interface that is

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going to describe the very distinct coupling between this particular subject and the event data that

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we expect to receive with it.

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So back inside my editor once again inside the events directory.

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I'm going to make a new file called Ticket created event dot t yes at the very top we're going to import

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that into we just created so subjects from subjects we're then going to create an export and interface

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that we're going to call ticket created events.

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So again this is where we're going to set up this very tight coupling.

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We're going to say that there is going to be a very tight coupling between this very specific subject

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name and this structure of data.

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We went to then figure out how to enforce that coupling inside of our actual listener so inside this

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interface we're gonna say that we expect there to be an event at some point time that indicates that

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a ticket was just created the subject for this event will be of type subject start to get created and

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the data that we expect to see inside that event is going to be an idea that is a string a title that

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is a string any price that is a number.

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So again this is where we set up the coupling between this very specific subject and this structure

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of data we're going to eventually create interfaces just like the one right here to describe all the

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different types of events we eventually expect to have inside our application.

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So for example we might have a ticket updated event a order created order cancels order whatever else

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may we have a payment success event or payment failed event every different event we ever expect to

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have inside our application.

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We're going to create a different interface for it.

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And again that's going to make sure that typescript can step in and make sure that we have some matching

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subject and data inside of one of our custom listeners.

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We put together OK.

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So we've now got the listing of all the possible subjects.

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We've got the interface that describes the coupling of one particular subject with the structure of

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data.

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Now last thing we have to do is teach typescript how to somehow do some verification and make sure that

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when we put our custom listener together like this one right here we need to make sure that typescript

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understands that needs to check and make sure that this subject right here matches up with the type

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of data argument we have right there.

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So we'll take care of that in the next video.