This document provides an overview of using Realm as a mobile database solution instead of SQLite. Some key points: - Realm stores objects rather than rows/tables and has no boilerplate code for common SQLite tasks like SQL queries. - Objects are defined by creating RealmObject subclasses with getter/setter properties. These objects can then be stored, queried, and related to each other in the Realm database. - Relationships between objects can be defined to support one-to-many and many-to-many relationships. Objects are queried using a fluent query language rather than raw SQL. - Realm uses transactions to ensure data integrity. Objects are added/updated by beginning a transaction, making changes

1. Realm
HowILearnedto
StopWorrying
andLovemyApp
Database
or

2. Sergi Martínez
Android Developer at Schibsted Spain
Android GDE
@sergiandreplace

3. The usual stuff
My big server
My big database
My mobile app
My little
database
My
nice
API
The internet!

4. The usual stuff
My big server
My big database
My mobile app
My little
database
My
nice
API
The internet!
This tries to mimic this

5. The usual stuff
My big server
My big database
My mobile app
My little
database
My
nice
API
The internet!
Here We only need
to cache entities

6. The initial solution
SQLite

7. SQLite
SQL language
Relationships
Non-java data types
SQL Queries
SQL stuff

8. SQLite
SQL language
Relationships
Non-java data types
SQL Queries
SQL stuff
Do we need these?

9. SQLite
SQL language
Relationships
Non-java data types
SQL Queries
SQL stuff
Do we need these?
Really?

10. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc

11. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc
Boilerplate

12. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc
Boilerplate
Boilerplate

13. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc
Boilerplate
Boilerplate
OH! Wow! So much boilerplate

14. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc
Boilerplate
Boilerplate
OH! Wow! So much boilerplate
“Hard” to create. Excessive coupling with
UI

15. Also...
SQLDbHelper
SQL Queries
Content Providers
Loaders
etc
Boilerplate
Boilerplate
OH! Wow! So much boilerplate
“Hard” to create. Excessive coupling with
UI
Probably… more boilerplate

16. Let’s try something different… Realm
It stores objects
Hierarchical relationships (sort of)
No boilerplate (just probably mappers)
Fast!
Reduces dev time drastically

17. Adding Realm to your project
Your project build.gradle
buildscript {
repositories {
jcenter()
}
dependencies {
classpath "io.realm:realm-gradle-plugin:0.89.0"
}
}
apply plugin: 'realm-android'
Your app build.gradle

18. Realm Objects
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getEyes() { return eyes; }
public void setEyes(int eyes) { this.eyes = eyes; }
public boolean hasGoggles() { return goggles; }
public void setGoggles(boolean goggles) { this.goggles = goggles; }
}

19. Realm Objects
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getEyes() { return eyes; }
public void setEyes(int eyes) { this.eyes = eyes; }
public boolean hasGoggles() { return goggles; }
public void setGoggles(boolean goggles) { this.goggles = goggles; }
}
Must extend RealmObject

20. Realm Objects
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getEyes() { return eyes; }
public void setEyes(int eyes) { this.eyes = eyes; }
public boolean hasGoggles() { return goggles; }
public void setGoggles(boolean goggles) { this.goggles = goggles; }
}
Must extend RealmObject
Not exactly true since last thursday (#$%@!). More later...

21. Realm Objects
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getEyes() { return eyes; }
public void setEyes(int eyes) { this.eyes = eyes; }
public boolean hasGoggles() { return goggles; }
public void setGoggles(boolean goggles) { this.goggles = goggles; }
}
Object members that will be stored
More on types later

22. Realm Objects
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public int getEyes() { return eyes; }
public void setEyes(int eyes) { this.eyes = eyes; }
public boolean hasGoggles() { return goggles; }
public void setGoggles(boolean goggles) { this.goggles = goggles; }
}
Usual getters and setters

23. Supported data types
boolean/Boolean
byte/Byte
short/Short
int/Integer
long/Long
float/Float
double/Double
String
Date
Byte[]

24. Storing an object
realm.beginTransaction();
Minion minion = realm.createObject(Minion.class);
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.commitTransaction();
realm.cancelTransaction();
or
First, we start a transaction

25. Storing an object
realm.beginTransaction();
Minion minion = realm.createObject(Minion.class);
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.commitTransaction();
realm.cancelTransaction();
or
Then we create an instance inside our realm

26. Storing an object
realm.beginTransaction();
Minion minion = realm.createObject(Minion.class);
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.commitTransaction();
realm.cancelTransaction();
or
We set the values

27. Storing an object
realm.beginTransaction();
Minion minion = realm.createObject(Minion.class);
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.commitTransaction();
realm.cancelTransaction();
or
And commit the transaction. Then, our changes are saved

28. Storing an object
realm.beginTransaction();
Minion minion = realm.createObject(Minion.class);
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.commitTransaction();
realm.cancelTransaction();
or
Or we cancel the transaction and the new object is discarded

29. Storing an object - II
Minion minion = new Minion();
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.beginTransaction();
realm.copyToRealm(minion);
realm.commitTransaction();
Another way. We create the object outside the realm

30. Storing an object - II
Minion minion = new Minion();
minion.setName("Bob");
minion.setEyes(1);
minion.setGoggles(true);
realm.beginTransaction();
realm.copyToRealm(minion);
realm.commitTransaction();
Then, we begin a transaction, copy the object into the realm, and commit

31. Obtaining your Realm
First, create your Realm configuration
RealmConfiguration config = new RealmConfiguration.Builder(context)
.name("myrealm.realm")
.encryptionKey(getKey())
.schemaVersion(42)
.setModules(new MySchemaModule())
.migration(new MyMigration())
.build();

32. Obtaining your Realm
Then, get an instance
RealmConfiguration config = new RealmConfiguration.Builder(context)
.name("myrealm.realm")
.encryptionKey(getKey())
.schemaVersion(42)
.setModules(new MySchemaModule())
.migration(new MyMigration())
.build();
Realm myRealm = Realm.getInstance(config);

33. Obtaining your Realm
Or use the default Realm Instance
RealmConfiguration config = new RealmConfiguration.Builder(context)
.name("myrealm.realm")
.encryptionKey(getKey())
.schemaVersion(42)
.setModules(new MySchemaModule())
.migration(new MyMigration())
.build();
Realm.setDefaultConfiguration(config);
And obtain it anywhere
Realm realm = Realm.getDefaultInstance();
// Stuff
realm.close();

34. Close your Realms
For each
Realm.getDefaultInstance()
or
Realm.getInstance()
you must execute realm.close() at the end

35. Querying a Realm
Realm uses fluent syntax. Just create a RealmQuery object based on the Realm class you want
RealmQuery<Minion> query = realm.where(Minion.class);
Add operations and filters and execute
RealmResults<Minion> results = query.equalTo(“name”, “Bob”).findAll();
Do something with the result
for (Minion minion:results) {
…. //Do stuff
}

36. Query operators
between()
greaterThan()
lessThan()
greaterThanOrEqual()
lessThanOrEqual()
equalTo()
notEqualTo()
contains()
beginsWith()
endsWith()

37. Annotations
@Index
@PrimaryKey
@Ignore
@Required

38. Relationships - 1:N
Just have a RealmObject with a RealmObject
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
private Banana banana
//Getters, setters and so on
}
Public class Banana extends RealmObject {
…
}

39. Storing 1:N related objects
realm.beginTransaction()
Banana banana = realm.createObject(Banana.class);
banana.setSomething…
Minion minion = realm.createObject(Minion.class);
minion.setName(“Bob”);
minion.setBanana(banana);
realm.writeTransaction();

40. Relationships - M:N
Just have a RealmObject with a List<? extends RealmObject>
public class Minion extends RealmObject {
private String name;
private int eyes;
private boolean goggles;
private RealmList<Banana> bananas
//Getters, setters and so on
}
Public class Banana extends RealmObject {
…
}

41. Storing M:N related objects
realm.beginTransaction()
Banana banana = realm.createObject(Banana.class);
banana.setSomething…
Minion minion = realm.createObject(Minion.class);
minion.setName(“Bob”);
minion.getBananas().add(banana);
realm.writeTransaction();

42. Querying M:N related objects
RealmResults<Minion> minions = realm.where(Minions.class)
.equalTo("banana.size", "big")
.findAll();

43. Threading
Each Realm should live in the same Thread is has been created
You can’t pass Realms between threads
Realms are automatically updated between threads IF they are in threads with a Looper
Otherwise… Realm.refresh()

44. More things
Dynamic realms
Schemas
Migrations
UI controls
Browsers
etc...

45. Brand new changes
This week on Realm:
RealmModel interface + static methods
RealmCollection/RealmOrderedCollection Interfaces
Primary keys can be null!

46. How I use it
public abstract class VOBaseMapper<V extends RealmObject,E> {
public abstract V toVO(E entity);
public abstract E toEntity(V vo) ;
public RealmList<V> toVO(List<E> entities) {
RealmList<V> realmList=new RealmList<V>();
for (E entity:entities) {
realmList.add(toVO(entity));
}
return realmList;
}

47. How I use it
public List<E> toEntity(RealmList<V> vos) {
List<E> applicationEntityList = new ArrayList<>();
for(V vo :vos){
applicationEntityList.add(toEntity(vo));
}
return applicationEntityList;
}
public List<E> toEntity(RealmResults<V> vos) {
List<E> applicationEntityList = new ArrayList<>();
for(V vo :vos){
applicationEntityList.add(toEntity(vo));
}
return applicationEntityList;
}
}

48. How I use it
public class UserVOMapper extends VOBaseMapper<UserVO,User > {
private User user;
@Override
public UserVO toVO(User user) {
UserVO vo=new UserVO();
vo.setName(user.name);
vo.setEmail(user.email);
return vo;
}
@Override
public User toEntity(UserVO vo) {
User user= new User();
user.name=vo.getName();
user.email=vo.getEmail();
return user;
}
}

49. And that’s not all
But enough for today.
Questions?

50. @sergiandreplace
Thanks for coming