Intro to MVC

Lesson Objectives

Define MVC and explain why it matters
Move our data into a separate file
Move our presentation code into an EJS file

Define MVC and explain why it matters

One of the core tenants of good programming is to compartmentalize your code
Already our code is getting a little messy
- we have data, app instantiation (listening), and routes all in one file
One way to keep an app from getting messy is to separate it out into three sections
- Models
  - data (javascript variables)
- Views
  - how the data is displayed to the user (HTML)
- Controllers
  - the glue that connects the models with the views
This allows various developers to divide up a large code base
- minimizes likelihood of developers overwriting each others code
- allows developers to specialize
  - one can focus just on getting good with dealing with data
  - one can focus just on getting good with html
  - one can focus just on getting good with connecting the two
Think of MVC as a restaurant
- Models are the cook
  - prepares food/data
- Views are the customer
  - consumes food/data
- Controllers are the waiter
  - brings food from cook to customer
  - has no idea how food/data is prepared
  - has no idea how the food/data is consumed

Move our data into a separate file

Create a directory called models inside our app directory
Inside /models, create a data file named fruits.js

Put your fruits variable in there

const fruits = [
    {
        name:'apple',
        color: 'red',
        readyToEat: true
    },
    {
        name:'pear',
        color: 'green',
        readyToEat: false
    },
    {
        name:'banana',
        color: 'yellow',
        readyToEat: true
    }
];

We now require that file in the original server.js

const fruits = require('./models/fruits.js'); //NOTE: it must start with ./ if it's just a file, not an NPM package

But, we could have multiple variables in our /models/fruits.js file.
- How does javascript know which variable in /models/fruits.js to assign to the fruits const in server.js (the result of the require() statment)?
- We must tell javascript which variable we want to be the result of the require() statement in server.js
```
//at the bottom of /models/fruits.js
module.exports = fruits;
```

Move our presentation code into an EJS file

Now we want to move our View code (HTML) into a separate file just like we did with the data

Install the NPM package EJS (Embedded JavaScript)
- this is a templating library that allows us to mix data into our html
- the HTML will change based on the data!
- npm install ejs
Create a views directory inside our app directory
Inside /views, create a file called show.ejs
- this will be the html for our show route

Put some html into show.ejs

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Fruits App</title>
    </head>
    <body>
        <h1>Fruits show page</h1>
    </body>
</html>

Now, instead of res.send('some text'), we can call res.render('show.ejs')
- express will know to look inside the /views directory
- it will send the html in the show.ejs file as a response
```
app.get('/fruits/:indexOfFruitsArray', (req, res) => {
    res.render('show.ejs');
});        
```

Now lets mix our data into our HTML

Our route is acting like the controller now. Let's gather the data and pass it to the view

app.get('/fruits/:indexOfFruitsArray', (req, res) => {
    res.render('show.ejs', { //second param must be an object
        fruit: fruits[req.params.indexOfFruitsArray] //there will be a variable available inside the ejs file called fruit, its value is fruits[req.params.indexOfFruitsArray]
    });
});

Access the data in the view:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Fruits App</title>
    </head>
    <body>
        <h1>Fruits show page</h1>
        The <%=fruit.name; %> is  <%=fruit.color; %>.
        <% if(fruit.readyToEat === true){ %>
            It is ready to eat
        <% } else { %>
            It is not ready to eat
        <% } %>
    </body>
</html>

Note that there are two types of new tags
- <% %> run some javascript
- <%= %> run some javascript and insert the result of the javascript into the HTML

Update Index Route:

Update the index route in server.js:

app.get('/fruits/', (request, response) => {
    response.render(
        'index.ejs',
        {
            allFruits:fruits
        }
    );
});

Create an index.ejs file:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>Fruits App</title>
    </head>
    <body>
        <h1>Fruits index page</h1>
        <ul>
            <% for(let i = 0; i < allFruits.length; i++) { %>
                <li>
                    <a href="/fruits/<%=i%>"><%=allFruits[i].name %></a>
                </li>
            <% } %>
        </ul>
    </body>
</html>

Add a link back to the index route in show.ejs: