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In this video we're going to show you a slightly better way of riding out this ability is our function

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so that's not a separate standalone function.

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Instead we're going to get this thing built in or included with our user model the end goal here.

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What we're really going forward is to kind of cut to the chase.

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What I really want to do is used to say user dot build and then pass in an email and a password.

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The nice thing about this approach.

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If we could get it to work we no longer have to export a separate thing from this file and create a

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new user is kind of a natural thing we say user built.

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Build me a new user create a new one.

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It makes a lot of sense and it possibly even makes more sense than this approach over here where we

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say new user it's just all a bit easier to understand what is going on because we've got that build

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method named in there.

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So that's the refactor or the change we're going to make we're going to figure out how to build in or

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include this build user function on the User model itself so let me show you how we do that to add in

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a new method to our user model.

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So really that thing right there we're going to take a look back at our user schema right above where

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we create the new user or the User model.

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I'm going to write out user schema dot statics dot built and then I'm going to assign to that the same

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function that we wrote down a little bit ago.

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So this one right here.

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So we'll say adders is user adders and then return new user with adders.

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I'm now going to remove the old build the user and delete it from the expert list as well.

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So this is how we get a custom function built into a model we add it to this statics property on our

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schema now it definitely appears like this works.

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But let's try to actually use it.

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So a quick test right here I'll say user dot builds and sure enough I still end up getting an error.

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So this is yet another point at which getting TypeScript and Mongoose to work together is just a little

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bit awkward typescript does not understand what it means to assign a property to the statics object

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if we were making use of JavaScript everything would work just fine and to be truthful with you.

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This right here it is accurate code everything we have.

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Totally accurate.

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This is how we add a function to a use it to a model in Mongoose but typescript just doesn't understand

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that we have to give a little bit more information to typescript.

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So let me show you how we're going to fix this.

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I'm going to go back up to the top of the file again.

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I'm going to add in yet another comment and I'm going to say an interface that describes the

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properties that a user model has.

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So we're gonna write out an interface that's going to essentially tell typescript that there's going

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to be a build function available on this user model.

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We're going to say that there is a built function and we're gonna tell it what arguments are required

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to call it as well I'm going to write out interface user model I'm gonna say extends Mongoose dot model

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we're going to take a look at this existing interface right here I know there's an error there don't

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worry about that we'll fix up in just a moment I want to take all the properties that already exist

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on that interface I want to add them into this new one that we are creating and I want to add in some

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new properties on top that we are getting an error from this right now to fix that error we're gonna

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put in a set of angled brackets and then write any inside there we're gonna come back and discuss what's

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going on with that just a moment but right now we'll just leave in any then on this interface we're

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going to write in that build method.

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And again this is going to tell typescript about the instance of the build method and what properties

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it accepts inside of here.

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We'll write out build it's going to take an argument called adders.

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It must be of type user adders

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and from that we are going to return right now.

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Just any we're gonna come back and fix up that any as well in just a moment.

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So now that we've got this interface put together typescript can understand about what a real user model

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is.

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All we have to do is really tell typescript about the existence of this interface so I'm going to go

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back down to where we created our Mongoose model right here.

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I'm gonna put a set of angled brackets after model I'm gonna write an any and then user model and as

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soon as I do so you'll notice that the era at year changes typescript is no longer complaining that

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we're trying to access a build property on user anymore.

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Instead it's transferred the air to the set of really braces.

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So now it's telling us hey if you want to create a new user or if you want to call this build method

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you must pass in an email and a password.

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Now if I put in an email of test at test dot com and a password of password those errors go away so

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we've now told typescript about this additional property that the user model is going to have a definite

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looks like it works out.

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Now even though this works unfortunately we just introduced a bunch of kind of mystery syntax right

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here right here and we've got that any right there as well.

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So again it works but while we've introduced a bit more confusion and unfortunately this is kind of

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that stuff.

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As mentioned earlier we're getting the typescript and Mongoose to work together involves a little bit

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of kind of crazy code.

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It definitely works and we've got some awesome type checking included now but there's kind of a mental

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cost so to speak.

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Included with it in addition to that we have really only solved issue number one right now.

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We have not really solved anything related to issue number two where we needed to somehow tell typescript

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and Mongoose that the set of properties that we pass into creating a new user are different than the

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properties that end up on a user OK.

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So still a little bit to get through here.

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Right now I'm going to delete that user dot build because I was just a quick test.

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I'm going to save this file.

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We're gonna take a quick pause and continue again in just a moment.