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Well come back in this video going to show you how we can set up an association a one to many association

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between two mongoose models by embedding data and we're going to be working with user and post.

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So this will be like a Facebook or blog app where we have a user and a user can have many posts but

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a post belongs to one user and we're not going to be creating an actual app here with routes and templates

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.

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We're just going to focus on the data and the data modeling.

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So I'm going to get started by making a new file inside of this associations directory that I made.

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You can do this wherever you want.

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It's going to be a single file and I'll call it embed dot J.S. and I'll open that up and inside of here

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I'll require mongoose which I haven't installed yet so I'll do that next and PM install mongoose and

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that will take a moment.

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There we go.

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Let's make some space.

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And once we require it the next thing we want to do is connect to a database so mongoose does connect

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and this is totally up to us again the name of the database but it has to be Mangu D-B colon slash slash

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local host slash and roll call.

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This blog demo just like that and save.

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OK so now we need to define two models we have user and we have a post.

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The user will just have an e-mail and a name and a post.

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It's going to have a title and then a content.

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The actual post itself.

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So we'll start with the user need to define the schema.

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So far user schema equals new mongoose schema and then we're going to have email which is a string and

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name which is a string just like that.

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And then we'll create the model so far.

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User equals mongoose model user.

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The Cingular version and then user schema is what we're building it from.

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And we'll save that.

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OK.

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Now let's move on to the post.

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So we're going to create another schema this time var post schema equals new mongoose schema and then

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each post has a title that is a string and content that will just make a string as well.

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And then we also need to turn that into a model var post model equals mongoose stop model post comma

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post schema.

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Right.

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So we have two schema set up two models.

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Let's make a little bit of room here.

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So we have our posts and we have our users.

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And let's just try running this.

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Make sure we don't have any syntax errors to start node embed Dutcher Yes.

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Looks good.

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Now let's go and create a single user just to make sure our model works.

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So at the very bottom done here I'm going to make a new user so we'll just call it our new user equals

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new user and then we'll pass an email and email will be Charlie at around Edu and name will be Charlie

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Brown just like that.

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And then what saves a new user to save.

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And then we'll add in our callback with the error and then the data coming back which is hopefully our

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user and then not just you.

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If error cancels out log error.

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Else we're going to cancel that log user.

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So so far no associations.

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I'm just testing to see if our user model works.

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So let's run this node embed Dutchesse and we get our user back with the ID that was automatically generated

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name and email.

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Great let's try the same thing with post so comment that out so we don't get another user and we're

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going to do our new post equals new post and a Post has a title and the title of the post will be reflections

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on apples and the text of that post or the content.

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I think we called it yes content will be.

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They are delicious.

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All right.

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Great blog post there.

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We'll save make sure everything's good and then we're going to actually do a new post that save us and

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the callback again by now.

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Hopefully you're getting comfortable with this pattern because you're seeing it nonstop where are passing

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this call callback to mongoose.

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Every time we do anything with Monga is finding creating saving updating eventually removing eventually

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we need to pass in a callback with the error as the first parameter and then the data as the second

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one.

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All right.

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So if error cancels out log ever otherwise come to that blog post make sure these both work.

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Let's try it and we run into a small issue.

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It's telling us that post is not defined when we're trying to make a new post.

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And the most logical reason for that to happen would be if we named our model something other than post

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.

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And what do you know.

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We named it post model and by we I mean that I named it incorrectly.

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So let's go with post.

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We could have kept it as post model and then changed it here.

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But it's definitely conventional to have it just be the name of what you're making you don't need to

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have model in there you don't need any extra characters just the name of the model itself or of the

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entity post with a capital P..

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All right so that matches now.

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Right we have post and post here.

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Let's try this again and this time it adds a new post content.

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They are delicious title reflections on apples.

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OK now that we've made sure that our two models are working correctly we can make a post and we can

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make a user.

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But currently they have nothing to do with one another and we want them to have a relationship remember

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that we want a user to have or to own many posts and a post will belong to one user.

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So that's a one to many relationship.

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And the way that I'm going to show you to accomplish that is by embedding data instead of a user schema

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.

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So it's going to look like this.

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Then I'll explain it in just a moment.

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We're going to have a post's attribute inside the user and inside the Post's attribute.

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We're going to have a bunch of posts and to make that work we need to add the post schema inside of

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an array.

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So rather than making posts a string or a number or a boolean we're telling mongoose we want it to be

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a list an array of posts and we have to write post schema which is a little bit confusing honestly.

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I wish that it was just post the name of the model but it's just the way that it is.

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It needs to be the name of the schema and we have one other issue which is that if we run this right

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now it's not going to know what post-chemo is and that's because we're defining it second.

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So if we're embedding the data we need to define it first.

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So we define the post schema and the post model and then we define the user schema and inside the user

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schema we're adding an attribute called posts which is an array of posts.

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So if we do that our data will look something like this or we'll have a name for a user let's do e-mail

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and I'll just do jibberish a name and then we'll also have posts and posts an array.

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And inside that array we have multiple posts so each post has a title and content and a user can have

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many posts just like that.

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And so for every post that we get it will be a new post instead of the posts attribute on a particular

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user.

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So let's get that going.

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Let's create a user and then I'll show you how we can add a post to that user so we can just use our

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.

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Charlie Brown here.

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New User equals Charlie Brown.

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Although I'll change some of the e-mails and names because we already have Charlie Brown in the database

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.

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Let's go with are my any at Hogwarts edu.

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And then we'll change this to be my auntie Granger.

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All right.

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So we have a new user and then to add a post to that user.

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All they have to do is write new user posts that push because it's an array.

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And I push in a new post and a Post has a title and the title of my next post will be how to brew poly

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juice potion and then the content will be just kidding.

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The potions class to learn it all right.

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Whatever it doesn't really matter.

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So we have a title and some content and then we're going to push this post into new user which we defined

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up here.

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And the last thing we need to do is save new user.

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So a new user that save like that.

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And we actually already have this written so I'll just reuse that and uncomment that and this will try

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and save it.

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If there's an error it will let us know.

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Otherwise it will show us the user and then comment out all this stuff down here about posts and just

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save that and let's see what happens.

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So we have our post schema which you defined then we have the user schema and the new part is right

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here where we have an array of posts inside of the user.

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And then we're creating a new user and pushing into that post right.

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Let's give it a shot.

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OK.

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And we get back this user that we're printing here emails reminding at Hogwarts name it's Hermione Granger

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and then instead of posts we have a new post.

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So that's working just fine.

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Now let's try something else where I'm going to comment all this out and rather than creating a new

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user let's retrieve the existing user.

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So I'm going to retrieve her mining.

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So I'll do that with user find.

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And I'm going to use find one.

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Otherwise find will give me an array and I just want one thing back.

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So we're going to do you don't find one will find where name is Hermione Granger and then we'll do our

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standard callback error and we'll just call this user.

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Hopefully you're getting comfortable with that right now.

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This right here the callback that we write pretty much every time we do anything with Mongoose and then

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we'll just do it.

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If ever

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counsel dialog error and then Otherwise

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we'll constantly bug user and I have an extra bracket I need to get rid of every go.

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So this is just to find her my new back nothing new.

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We're just finding a new user and it works.

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We get the user coming back.

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Her name is her mind she e-mails her money at Hogwarts.

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OK now let's suppose I want to add another post because this is supposed to be a one to many.

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So one user can have multiple posts.

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Let's do that now.

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So inside of the else once we find the user We're going to run some code to add in a new post and then

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that looks like this user posts up push just like before and this time will push in another post so

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we'll push in title and the title is three things.

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I really hate and the content will be all the more all the more.

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And Voldemort.

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All right very creative post there remind me and we'll go ahead and save this.

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So we still need to do a user save and then we'll add in our callback afterwards.

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Another one of these error.

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And we'll just call this user again.

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And instead of here will do if error console log error otherwise cancel out log user.

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All right so this is what some people would call callback.

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Hell we have a lot of callbacks here.

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We have this first one which is finding her mind the finding that user that we're getting and then we're

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pushing in a new post.

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But that doesn't actually add to the database.

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We then have to save it.

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And so we do user save and this user right here.

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These two are referring to the user that comes back when we find her mind the the first time and then

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we're saving and then this user is referring to what comes back from the save.

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So this user here now has the new post added to it and save to the database.

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It's the data that is coming back to us from Mongo and then we're printing it out.

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Let's try it now.

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So let me get rid of this first counterplot log.

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Just leave it like that.

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Let's clear make sure we don't have any other code running that's going to interfere with our accounts

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about logs.

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Let's run it.

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All right.

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So what we see is that we're now printing out a single user Hermione that has two posts as first one

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and the second one and they're both stored inside of the post attribute on the single user.

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So it's one to many.

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OK.

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So that's all I want to show.

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Let's just reflect on this briefly.

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So we started by sitting at Mongoose and we have two models and they were independent to start.

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And then we associated them by adding this post schema array to the user schema.

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So now a user has an array of posts and it starts empty.

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But then we added to it by pushing in post dot push and then we saved in the next video going to show

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you another way of associating data using what are called object references.