In this talk I would like to share my experience of using this new mobile database with great potential. We will see which are the major differences compared to SQLite and what makes Realm very fast so as to be called "in realtime". We develop a realtime multiplatform collaborative app starting from scratch, using the latest features introduced by Xamarin Forms to improve the responsiveness. Your viewmodels and bindings for sure will thank you! :-)

1. ROME - APRIL 13/14 2018
Andrea Ceroni
Go reactive with Realm and
Xamarin Forms

2. Andrea Ceroni
andrea.ceroni@elfo.net
@andrekiba
http://www.linkedin.com/in/andreaceroni
elfo.net klabcommunity.org

3. Realm + Xamarin.Forms

4. Xamarin.Forms

5. cosa è Realm??
Reactive Mobile Database
with Live Objects

6. caratteristiche
non è un ORM costruito su SQLite o simili
non è un Key-Value store (JSON) ma un db a tutti gli
effetti
completamente riscritto, core in C++ (open source)
Swift, Objective-C, Java, JavaScript
.NET con Xamarin (iOS, Android, Mac, UWP, .NET
Framework)
client + server (pensato per essere offline first)

7. var realm =
Realm.GetInstance(config);
ok ma come si presenta?

8. perchè Realm

9. MVCC (multiversion concurrency
control)
R
A B
C D E
V11)
R
A B
C D E
V12)
R1
A1
C1
V2
R1
A1 B
C1 D E
V23)
R
A C
garbag
e

10. zero copy e native links
native objects
ORM traduce in
istruzioni SQL
crea
connessione DB
invia le istruzioni al
disco
esegui la
query
leggi i dati
deserializza e
copia in
formato
intermedio in
memoria
ritorna gli
oggetti finali
copia in memoria in
formato appropriato
per il linguaggio
native objects realm db file
virtual memory
mapped
native links

11. lazy loading
non si può leggere meno di una "pagina"
però le proprietà sono gruppate "in verticale"
le proprietà non utilizzare non vengono lette
si evitano inutili accessi al disco

12. 4 concepts
transactions
objects
modify
notifications
trigger
queries
make up
UI events,
network,
...

13. objects
public class Dog : RealmObject
{
[MapTo("name")]
[Required]
public string Name { get; set; }
public int Age { get; set; }
public Person Owner { get; }
}
public class Person : RealmObject
{
[PrimaryKey]
public int Id { get; set; }
public string Name { get; set; }
public IList<Dog> Dogs { get; }
}
to one
to many
inverse
[Backlink(nameof(Dog.Owner))]
public IQueryable<Dog> Dogs { get;
}

14. queries
var artu = realm.Find<Dog>(6);
IQueryable<Dog> puppies = realm.All<Dog>()
.Where(d => d.Age < 2);
var mila = realm.All<Dog>()
.FirstOrDefault(d => d.Name == "Mila");
https://realm.io/docs/dotnet/latest/api/linqsupport.html

15. notifications
realm.RealmChanged += (s, e) =>
{
//do something
}
var subscription = realm.All<Dog>()
.SubscribeForNotifications((sender, changes, error) =>
{
//cosa è stato inserito, elimintato, modificato
});
//later
subscription.Dispose();
var mila = new Dog();
realm.Write(() => realm.Add(mila));
mila.PropertyChanged += (sender, e) =>
{
//do something
}

16. transactions
var realm = Realm.GetInstance(configuration);
realm.Write(() =>
{
var andre = realm.Add(new Person()
{
Id = 6,
Name = "Andrea"
});
var mila = new Dog()
{
Name = "mila",
Age = 1,
}
andre.Dogs.Add(mila);
mila.Owner = andre;
});

17. Realm Mobile Platform
Realm Database + Realm Object Server

18. Realm Object Server
https://realm.io/products/realm-studio/

19. REST sync

20. 2-way sync

21. autenticazione e syncconfiguration
var credentials = Credentials.UsernamePassword("username", "pass");
var authUrl = new Uri("http://realmAuthServerAddress:9080");
var user = await User.LoginAsync(creadentials, authUrl);
var serverUrl = new Uri("realm://realmServerAddress:9080/~/default");
var syncConfig = new SyncConfiguration(user, serverUrl);
var realm = Realm.GetInstance(syncConfig);
var realm = await Realm.GetInstanceAsync(syncConfig);

22. Demo

23. realm.All<Question>()
.SubscribeForNotifications((...) =>
{
if(iKnowTheAnswer)
Answer();
});

24. Grazi
e!
andrea.ceroni@elfo.net
@andrekiba
http://github.com/andrekiba
http://www.linkedin.com/in/andreaceroni
https://creativecommons.org/licenses/by-nc-sa/3.0/