• Upgrade Guide

Migrating to MongoKitten 4

This guide will help users of MongoKitten 1.x, 2.x and 3.x to migrate to 4.x


The connection URL supports authSource, authMechanism, ssl, Replica Sets and Sharded Clusters. But if you prefer not using an URL you still can.

MongoKitten 4 has an object “ClientSettings” which separates out the settings from the server.

ClientSettings accepts one or more hosts. Multiple hosts should only be used for replica sets and sharded databases.

ClientSettings(host: ...) accepts a MongoHost. Which is manually creatable but is initializable using a String (literal).

The String needs to be formatted like this: subdomain.example.com:12345.

The ClientSettings then accepts sslSettings. sslSettings is an object that has 3 values. One for enabling or disabling SSL. The other 2 are for certificate and host validation.

SSLSettings is ExpressibleByBooleanLiteral, so true will enable SSL with secure defaults. false will not use SSL.

Last but not least ClientSettings accepts login details in the form of MongoCredentials.

This accepts a username, password and database. If you don’t know the authentication database (it’s not always the same database as the one you’re trying to access) you can leave it empty wil nil here.


The automatically parameter has been removed. MongoKitten will always connect automatically now and will always attempt to reconnect.

server.connect() has been removed for the same reason.

Documents and Values

The ~ operator has been removed because Values are now directly embeddable inside Documents/Dictionary literals.

let name = "Joannis"

let doc: Document = [
  "name" ~name,
  "name2": "Joannis"
  "subDoc": [
    "name": ~name

Will become

let name = "Joannis"

let doc: Document = [
  "name" name,
  "name2": "Joannis"
  "subDoc": [
    "name": name


Document subscripts can be chained in MongoKitten 4.

Bool(doc["subdoc"]["boolean"]) will get the value called “boolean” inside “subdoc” and will return a boolean if it’s representable as one, nil otherwise. String(doc["_id"]) will try to convert the value to a String. So Int(3) will become "3". A String will stay a String, and ObjectIds will represent themselves as a hexadecimal String.

Collection insertion

Collection now feels more like a sequence, so inserting has been simplified.

try collection.insert(contentsOf: [
    userJoannisDocument, userLaurentDocument, userRobbertDocument