MVC Pattern in Node - aakash14goplani/FullStack GitHub Wiki

Topics Covered

What is MVC
Flow of Request
Reading a file
Writing in a file

What is MVC

MVC pattern in Node

Article

Flow of Request

You create a route that handles certain request
```
router.get('/', (req, res, next) => {...});
```
You create a model that holds your data object that is to be presented on UI or used for internal logic processing. Model is basically a class with getter-setter to access properties of class.
You create a controller corresponding to your router i.e. if you have 5 route-paths then you have to create 5 different controllers to handles those requests. If you have configuration where multiple routes needs same action then you can assign a common controller.
- Controllers are basically middlewares. We replace the middleware logic earlier defined in routes with Controllers. this is the example of controller:
```
const Product = require('../models/product');
...
exports.getProducts = (req, res, next) => {
   res.render('shop/product-list', { 
      prods: products, 
      title: 'All Products', 
      path: '/'
   });
};
```
- We export our controllers, so that they can be later imported (mostly by router)
- We pass the render logic to the Controller that router used to handle previously.
- Here we can access data from Model
- And finally we display data to View stored in shop/product-list directory
Finally assign your controller to Router
```
const shopController = require('../controllers/shop');
...
router.get('/', shopController.getProducts);
```
- Important - that you just pass the method reference and don't execute it (getProducts())

Reading a file

const filePath = path.join(rootDirectory, 'path_to_file');
E.G.
const filePath = path.join(rootDirectory, 'data', 'products.json');

Simple function:

fileSystem.readFile(filePath, (error, fileContents) => {
   if (error) {
      // handle error
   } else {
      // contents of file ready
   }
});

First argument is to specify the path of file
Second argument is the function that returns:
- error
- file contents
Since this is async function, it does not return values instantaneously, so we need to wrap this in callback

const getProductsFromFile = (callback) => {
    fileSystem.readFile(filePath, (error, fileContents) => {
        if (error) {
            callback([]);
        } else {
            callback(JSON.parse(fileContents));
        }
    });
}
save() {
   getProductsFromFile(products => {
      products.push(this);
      fileSystem.writeFile(filePath, JSON.stringify(products), (error) => {
         if (error) {
            // process error
          }
      }); 
   });
}

Writing in a file

fileSystem.writeFile(filePath, JSON.stringify(products), (error) => {
   if (error) {
      // process error
   }
});

First argument is to specify the path of file
Second argument is the data to be written to file
Third argument is error function to be handled