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Question and Answer Schemas

Name: Question and Answer Schemas
Uploaded: 2016-06-30T16:07:12Z
Duration: 395 s
Description: In this lesson we will write the two schemas that will be responsible for creating our MongoDB documents.

6:35 with Andrew Chalkley and Joel Kraft

In this lesson we will write the two schemas that will be responsible for creating our MongoDB documents.

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Blog series about Modelling one-to-many (AKA parent-child) relationships in MongoDB:
6 Rules of Thumb for MongoDB Schema Design, By William Zola, Lead Technical Support Engineer at MongoDB: Part 1
Part 2
Part 3

MongoDB documentation on data modelling

MDN page detailing Array.prototype.sort

JavaScript Patterns, by Stoyan Stefanov, is a great book on writing solid JavaScript code. On page 134, Stoyan Stafanov shows how to write a recursive deep-extend function.

Also, studying source code is a great way to learn! Here's jQuery's implementation of $.extend.

Skip down to line 124 (the line may move, so you can also use the browser's find in page and type in 'extend' to see where it is defined (jQuery.extend = …).

Let's connect to our question and answer service application to Mongoose, and 0:01

build the schemas for our API. 0:05

The code for 0:08

our database connection will be similar to the code we wrote in our sandbox. 0:08

You can just copy and paste it over to the app.js file. 0:13

Let's open up mongoose_sandbox.js. 0:19

And copy the mongoose require and the connection code. 0:24

Paste it into the app.js right above the router. 0:37

Let's also change the database name to QA for question and answer. 0:42

Notice the call to the db.once method is still open. 0:50

So let's close it with a curly brackets, parentheses and a semicolon. 0:53

Before when we working in our sandbox, we put all of the database interaction 1:06

code inside the callback in this once method. 1:10

That would ensure that the code would only run after the database connection was open 1:14

and ready for business. 1:19

Here in the Express app we wouldn't need to worry about that. 1:21

All we want to do is log out once the open event occurs. 1:25

Setting up the Mongo connection is still asynchronous and 1:31

in fact the express app will normally finish setting up and start listening for 1:34

requests before the database is ready. 1:39

While it would be easy to assume that the requests made during this time 1:42

would be dropped, Mongoose actually stores them and 1:46

then runs them once the database is ready, which is extremely helpful. 1:49

Now that the connection code is in place, 1:54

let's set up the schemas in a separate file called models.js 1:57

Create the file in the root of the folder called models.js, 2:08

and at the top of the file let's put use strict, 2:14

And require Mongoose 2:22

And store the schema constructor as a local variable. 2:35

Now we're ready to write the schemas. 2:46

We'll need two schemas, a question and an answer schema. 2:49

Let's create a question schema. 2:53

As previously decided, we'll need a text property to hold the text of the question, 3:08

As well as a time for creation. 3:21

And then a rate to store the answers in. 3:26

The text and date properties are straightforward. 3:32

To let Mongoose know about the relationship between answers and 3:36

questions, we'll need to place the answer schema 3:40

as the only elements of an array on the question schema. 3:44

This is a signal to Mongoose that we want answer documents to be nested inside 3:48

question documents. 3:53

We haven't created an answer schema yet. 3:54

But when we do, let's call it AnswerSchema. 3:57

Before we create the answer schema, let's improve the createdAt property. 4:04

We know that we want to set this to the current date and 4:09

time when every question is created. 4:12

Mongoose can take care of that using an object to specify the default value. 4:15

Now whenever a question is created using this schema, the current dates and 4:32

time will automatically be supplied for this field. 4:36

Right now, 4:39

AnswerSchema is undefined, since we haven't declared the variable yet. 4:40

We should do this above the QuestionSchema so 4:45

it will be defined by the time QuestionSchema sees it. 4:48

We know we'll need a text attribute and a createdAt time. 5:04

We'll also put in updated app time. 5:21

Which will initially match createdAt. 5:29

Let's also provide votes which is a number, 5:31

And the default value should be 0. 5:40

Now we have the two schemas that are connected together. 5:48

At the bottom of the file we can create and export a question model. 5:52

Let's first create the model using Mongoose's model method. 5:58

We can then later import the question into our routes file to make use of it there. 6:22

Our API is coming along nicely in the next video we'll look at ways to make it 6:29

even better. 6:33

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Build a REST API With Express

Question and Answer Schemas

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