A mini project to practice relationships in Mongo.

##Objectives You'll create a simple set of schema revolving around Artists, their Songs, and a set of Tags that are associated with songs.

##Step 1: Create Schema

In server.js file, make sure you include Express and Mongoose as dependencies. Also, in server.js, initiliaze the connection to Mongo.

Here are the Mongoose models we'll create in our server.js:

####Artist

• name (string)
• bio (string)
• genres (array of unique strings)

####Song

• name (string)
• album (string)
• genre (string)
• releasedOn (date)
• isExplicit (boolean)

####Tag

• name (string, unique)

Create each of the models listed above. Put them each in their own file in a /models directory. Make sure you use module.exports so that we can require these models in our API.

Now, let's connect these models. Both will use references, not embedded relationships.

• Use a one-to-many relationship for Artist -> Song
• Use a many-to-many relationship for Song -> Tag

This should necessitate adding fields to our models to represent these relationships:

####Artist

• songs

####Song

• artist
• tags

####Tag

• songs

##Step 2: Create API Back in server.js, let's create the routes for our little API.

####POST /artists Save a new artist

####GET /artists Returns a list of artists with a songs attribute

Create an artist named Nelly with the following attributes:

{
  "name": "Nelly",
  "bio": "Cornell Iral Haynes, Jr., better known by his stage name, Nelly, is an American rapper, singer, songwriter, entrepreneur, investor and occasional actor from St. Louis, Missouri",
  "genres": ["hip hop","pop","R&B"]
}

####GET /artists/:id Returns the specified artist

####POST /artists/:id/songs Adds a new song for the given artist

Create a song for Nelly with the following attributes:

{
  "name": "Ride wit me", 
  "album": "Country Grammar", 
  "genre": "pop", 
  "releasedOn": "4-1-2001", 
  "isExplicit": false
}

When you're finished, a GET to /artists/:id for Nelly should return something like this:

[
  {
    "_id": "...",
    "name": "Nelly",
    "bio": "Cornell Iral Haynes, Jr., better known by his stage name, Nelly, is an American rapper, singer, songwriter, entrepreneur, investor and occasional actor from St. Louis, Missouri",
    "songs": [
      {
        "name": "Ride wit me", 
        "album": "Country Grammar", 
        "genre": "pop", 
        "releasedOn": "4-1-2001", 
        "isExplicit": false
      }
    ],
    "genres": ["hip hop","pop","R&B"]
  }
]

####GET /song/:id Returns song with associated tags (remember populate)

####POST /song/:id/tags Creates a tag (if it doesn't already exist) and associate it with the given song. Hint: To do this, you might want to utilize the findOneAndUpdate with the upsert option set to true.

Now test your app by POSTing some tags to "Ride wit me."

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