Server-Side Swift with MongoDB: Getting Started

Following Users

To make the follow button work, replace the return statement in followUser with the following:

return database[User.collection].updateOne( // 1
  where: "_id" == follower._id, // 2
  to: [
    "$push": [
      "following": account._id
    ]
  ] // 3
).map { _ in }

In this code, you’re:

1. Getting the users collection.
2. Specifying which user to update.
3. Updating the user.

Creating Posts

Now that you’re able to see posts, it’s time to create some of your own!

To create a post, you’ll change createPost. In MongoDB, the insert operation creates new entities in a collection. MongoKitten even provides a helper for encodable types such as TimelinePost.

Replace the return statement in createPost(_:inDatabase:) with the following, to add the post to its collection:

return database[TimelinePost.collection].insertEncoded(post).map { _ in }

This line will insert the new, encoded post into the timelineposts collection.
Create a post and refresh the website. Your new post will be on the top! But you’re not done yet.

As you might have noticed, users can upload images as part of their posts. Any service should store the files on the disk. However, this can be a complex task if you want to do it right. You’ll need to take care of access control and high availability, to name a few.

MongoDB already supports high availability and replication. And the code that calls MongoDB already makes access checks. To take advantage of this, you’ll use GridFS. GridFS is a standard that can store small files into MongoDB. Preferably you’ll keep the files as small as possible. It’s great for storing images or PDF invoices.

To use GridFS, you’ll need to create a GridFSBucket. You can then upload or download files from this bucket. To allow uploading files, replace the return statement in uploadFile(_:inDatabase:) with the following:

let id = ObjectId() // 1
let gridFS = GridFSBucket(in: database) // 2
return gridFS.upload(file, id: id).map { // 3
  return id // 4
}

In the code above, you:

1. Generate the file’s identifier.
2. Open the GridFS bucket in the selected database.
3. Upload the user’s file to GridFS.
4. Return the generated identifier.

Reading Uploaded Files

To share the file with users, the repository uses readFile(byId:inDatabase:). Like the example above, you’ll access file storage through a GridFS bucket. But instead of uploading a file, you’ll read the contents instead.

First, you must fetch the file from the GridFSBucket. The fetched GridFSFile does not contain the contents of the file data. Instead, it contains all metadata related to this file. This includes the filename, size and any custom data.

After fetching the GridFSFile, read the file’s contents using the file’s reader. Replace the return statement in readFile(byId:inDatabase:) with the following:

let gridFS = GridFSBucket(in: database) // 1

return gridFS.findFile(byId: id) // 2
  .flatMap { file in
    guard let file = file else { // 3
      return database.eventLoop.makeFailedFuture(Abort(.notFound))
    }
    
    return file.reader.readData() // 4
}

In the code above, you:

1. Get the Bucket
2. Find file by Id
3. Unwrap file, else throw an error
4. Read data and return

Build and restart the application. Then, create a new post and don’t forget to attach an image. You’ll see your new post in the timeline, including the image.

Congratulations! You’ve completed your first app with MongoDB and Server-Side Swift.

Where to Go From Here?

You can download the completed project files by clicking the Download Materials button at the top or bottom of the tutorial.

MongoDB has a lot of powerful features to offer. If you’re looking to expand upon those, I recommend reading the official documentation at mongodb.com.

If you want to learn more about developing web services in Server-Side Swift, our Server-Side Swift With Vapor book is a good starting place.

MongoDB is a powerful database. Are you excited to explore it more? Feel free to share your thoughts on MongoDB and MongoKitten in the discussion below!