`Codable` Usage in MongoSwift and MongoSwiftSync

There are a number of ways for users to leverage Codable via the driver’s API. One such example is through MongoCollection<T>. By default, MongoDatabase.collection returns a MongoCollection<BSONDocument>. Any find or aggregate method invocation on that returned collection would then return a MongoCursor<BSONDocument>, which when iterated returns a BSONDocument?:

Async/Await (recommended):

let collection = db.collection("person")

for try await person in try await collection.find(["occupation": "Software Engineer"]) {
    print(person["name"] ?? "nil")
}

try await collection.insertOne(["name": "New Hire", "occupation": "Doctor", "projects": []])

Async (EventLoopFutures):

let collection = db.collection("person")

collection.find(["occupation": "Software Engineer"]).flatMap { cursor in
    cursor.toArray()
}.map { docs in
    docs.forEach { person in
        print(person["name"] ?? "nil")
    }
}
collection.insertOne(["name": "New Hire", "occupation": "Doctor", "projects": []]).whenSuccess { _ in /* ... */ }

Sync

let collection = db.collection("person")

for person in try collection.find(["occupation": "Software Engineer"]) {
    print(try person.get()["name"] ?? "nil")
}
try collection.insertOne(["name": "New Hire", "occupation": "Doctor", "projects": []])

However, if the schema of the collection is known, Codable structs can be used to work with the data in a more type safe way. To facilitate this, the alternate collection(name:asType) method on MongoDatabase, which accepts a Codable generic type, can be used. The provided type defines the model for all the documents in that collection, and any cursor returned from find or aggregate on that collection will be generic over that type instead of BSONDocument. Iterating such cursors will automatically decode the result documents to the generic type specified. Similarly, insert on that collection will accept an instance of that type.

First, define custom types matching your collection schema:

struct Project: Codable {
    let id: BSON
    let title: String
}

struct Person: Codable {
    let name: String
    let occupation: String
    let projects: [Project]
}

let collection = db.collection("person", withType: Person.self)

Then, use your custom types along with the driver APIs:

Async/Await (recommended):

for try await person in try await collection.find(["occupation": "Software Engineer"]) {
    print(person.name)
}

try await collection.insertOne(Person(name: "New Hire", occupation: "Doctor", projects: []))

Async (EventLoopFutures):

collection.find(["occupation": "Software Engineer"]).flatMap { cursor in
    cursor.toArray()
}.map { docs in
    docs.forEach { person in
        print(person.name)
    }
}
collection.insertOne(Person(name: "New Hire", occupation: "Doctor", projects: [])).whenSuccess { _ in /* ... */ }

Sync

for person in try collection.find(["occupation": "Software Engineer"]) {
    print(try person.get().name)
}
try collection.insertOne(Person(name: "New Hire", occupation: "Doctor", projects: []))

This allows applications that interact with the database to use well-defined Swift types, resulting in clearer and less error-prone code. Similar things can be done with ChangeStream<T> and ChangeStreamEvent<T>.

Codable Usage in MongoSwift and MongoSwiftSync

`Codable` Usage in MongoSwift and MongoSwiftSync