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In this video.

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Let's talk about another important property or concept.

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When it comes to mongoose, it's what we call virtuous.

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So in Mongoose, a virtual property is a property that is not stored into the MongoDB.

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But instead, we use the virtual house to do what is called computation or add more logic to our document.

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So let me show you what I mean here.

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So back to the model.

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Let's open the user model.

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Let's take it that we want to find the number of posts a user has created.

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We can do it inside the root that is open, fetching, and then we can fetch a post by a user.

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And on that we can use the array method on it to get the total post created by a particular user.

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But we can achieve the same concept using what is called virtuous.

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So let me show you what I mean.

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So now let me collapse this one and let's come down here and let's say find the total post created by

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this user.

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So here we bring in the schema that is a user schema and we add what is called virtual grade.

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So this property is not going to be persisted into the document and save it into DB.

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But instead, upon fetching or querying, we can get back that property.

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So for this, let's call this one as post count and we add what is called dot gate.

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And for this we pass in a callback function.

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But for this we are going to use normal function because we want to use this keyword inside that.

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So here we go.

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Great.

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So how are you going to get it done?

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For the meantime, let's retain some static value, say 20.

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So with this one, when I make a request to find or to fetch a user, I will see a property called post

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count, which is equal to 20.

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So now let's check it out.

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When I hit ST for fetching all users, well, you can see that we don't have any property called post

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count unless we move further before we can see that property by default.

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Mongoose does not include virtual freehold when you convert a document to Jason, so to be able to get

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the actual property unless we add additional configuration to that particular model.

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So now as a second argument to the schema, that is this one, we come here and then we bring in objects.

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So here we pass in what is called to Jason and as an object and you bring in virtuous to true.

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So with this one to help us to get this property on the model upon fetching.

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So now let's see when we hit st let's look through the user.

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Let me collapse the post here and this time around you can see that we have the post count which is

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20, but it is nowhere to be found on the user model.

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That's a beauty of the virtuous.

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So to make it more dynamic instead of this one, we are going to use this.

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So this refers to the instance of this particular user.

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So if you console.log this, you can see that we are going to see this particular user that we have

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found inside our root is this instant.

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So now let me comment this one or let me just retain 30 here for the meantime, and let's make the request

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and let's check our terminal.

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And you can see that we have the entire user and we can access the post and we use the length on it.

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So here we go.

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Let's remove this one from here and we can make use of this dirt post dirt length.

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So moment of truth.

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So let's go ahead and then fetch all users and let's collect the post.

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And you can see that we have Post County.

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If I go ahead and create another post with the same title and description, let's fetch our users and

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let's see the post counts and it's from around.

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We have three post count how awesome it is so we can do more using the virtual and use this one a lot

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in my free word applications.

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All right, guys.

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So here ends the section about data modeling in Mongoose.

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We are going to build a couple of projects to reinforce our skills when it comes to data modeling,

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especially when we get to manage that project.