The document summarizes Realm, an open source database that allows developers to build mobile apps that work offline. Realm is widely adopted, with over 100k developers building apps on it and 40k of the world's most popular apps using Realm with over 2 billion installs. Realm databases are lightweight, embedded on the client, use an object-oriented data model, and support live objects that update automatically without polling. The document also provides details on Realm objects, queries, notifications, and the developers' vision for future enhancements.

1. Realm
Jason Flax | Lead Engineer, Realm Cocoa
Lee Maguire | Software Engineer, Realm Cocoa

2. 100k
developers
have built apps on Realm
40k
of the world’s most
popular apps
2bn
installs and counting
across all devices
Leading Apps are Built on
Realm:
Widely Adopted Open Source Database

3. Realm Database
● Works offline
● Lightweight, fully-featured
database that’s embedded on the
client
● Object-oriented data model; no
need to work with ORM
● Live Objects no need to write code
to check the client-side datastore
for changes in the user’s data
● Tight integration with SwiftUI
● Encryption is easy

4. Realm Database
The core concept of the Realm SDK is a
lightweight object container called a
Realm. Like a database, data in Realms
can be queried and filtered,
interconnected, and persisted. Unlike a
traditional database though, objects in
Realms are live and fully reactive.
● Represents an instance of a Realm
database container (can be a file, or in
memory)
● Data internally represented and
exposed as objects
● Relations are link lists / pointers
● ACID compliant, performant

5. Realm
Jason Flax | Lead Engineer, Realm Cocoa
Lee Maguire | Software Engineer, Realm Cocoa

6. Realm Object Classes are the Schema
import RealmSwift
class Dog: Object {
@objc dynamic var name = ""
@objc dynamic var age = 0
}
class Person: Object {
@objc dynamic var name = ""
@objc dynamic var dog: Dog?
let puppies = RealmSwift.List<Dog>()
}

7. Objects are Live and Auto-Updating
let myDog = Dog()
myDog.name = "Fido"
myDog.age = 1
try! realm.write {
realm.add(myDog)
}
let myPuppy = realm.objects(Dog.self).filter("age == 1").first
try! realm.write {
myPuppy!.age = 2
}
print("age of my dog: (myDog.age)") // => 2

8. Perform Complex Queries Across Objects
// Query using a predicate
var tanDogs = realm.objects(Dog.self)
.filter("color = 'tan' AND name BEGINSWITH 'B'")
// Query using an NSPredicate
let predicate = NSPredicate(format: "color = %@ AND name BEGINSWITH %@",
"tan", "B")
tanDogs = realm.objects(Dog.self).filter(predicate)

9. Listen to Object Changes to Simplify Your Architecture
let realm = try! Realm()
let myPuppy = realm.objects(Dog.self).filter("age == 1").first!
// Observe Realm Notifications
let token = myPuppy.observe { change in
// ... puppy age change will appear here
}
try! realm.write {
myPuppy.age = 3
}
// Finally
token.invalidate()

10. Bringing it all together
Modify Update Trigger
Events
Transactions Objects Queries Notifications
Transactions are the
only things that modify
state, and do so in a
threadsafe manner
Realm objects are
flexible, and can contain
any kind of data: objects,
lists, graphs, etc.
Queries are declarative
and are automatically
updated as the state
changes.
Any state change, be it
in queries or individual
objects, can be reacted
on to update UI or
trigger side effects.
class Dog: Object {
@objc dynamic var name = ""
@objc dynamic var age = 0
}
try! realm.write {
realm.add(myDog)
}
let puppies =
dogs.filter("age < 2")
myDog.observe { change in
viewController.updateUI()
}

11. What’s Next for Realm Cocoa?
● SwiftUI Enhancements with Property Wrappers
● Dictionaries, Sets, Mixed, & UUID Types
● Full-text Search
● Property Wrappers for Realm properties

12. Join Us!
● Give it a Try - https://docs.mongodb.com/realm/ios/install/
● Ask a Question - https://forums.realm.io/
● File an Issue - https://github.com/realm/realm-cocoa
● Connect with our Community -
https://live.mongodb.com/realm-global-community/
● Join our Team -
https://www.mongodb.com/careers/departments/engineering
● Tweet at us - https://twitter.com/realm?s=21

13. Thank you