Realm Mobile Database - An Introduction

Realm Mobile Database - An Introduction

• 1.
  Realm Mobile Database GeetikaGupta Software Consultant Knoldus Software LLP
• 2.
  AGENDA ➔ What is Realm ➔ Installation ➔ RealmModels ➔ Writes ➔ Queries ➔ Configuring Realm
• 3.
  What is Realm? ➔ Realm is a cross-platform mobile database, released in July, 2014. ➔ It is a data persistence solution designed specifically for mobile applications. ➔ Realm store data in a universal, table-based format ➔ It is simple as data is directly exposed as objects and queryable by code, removing the need for ORM's maintenance issues. ➔ Realm is faster than raw SQLite on common operations, while maintaining an extremely rich feature set.
• 4.
  Installation ➔ You can installrealm by adding the following class path dependency to the project level build.gradle file. buildscript { repositories { jcenter() } dependencies { compile 'io.realm:realm-android:0.87.4' } }
• 5.
  Models ➔ Realm model classesare created by extending the RealmObject base class. public class User extends RealmObject { private String name; private int age; } ➔ Realm supports the following field types: boolean, byte, short, int, long, float, double, String, Date and byte[]. The integer types byte, short, int, and long are all mapped to the same type (long) within Realm. ➔ Each model class that extends RealmObject describes the schema for the table in Realm.
• 6.
  Indexing Properties ➔ Theannotation @Index will add a search index to the field. ➔ It supports indexing on the following fields: String, byte, short, Int, long, boolean and Date
• 7.
  Primary Keys ➔ @PrimaryKeywill make the field primary key. ➔ It supports string or Integer (byte, short, int, or long) as primary keys. ➔ @PrimaryKey field implicitly sets the annotation @Index. ➔ copyToRealmOrUpdate() method is used to update an object having primary key. ➔ It looks for an existing object with the primary key and update it if found, If no object is found a new object is created. ➔ Calling copyToRealmOrUpdate() on classes without primary keys will throw an exception.
• 8.
  Transaction Blocks ➔ realm.beginTransaction(): Startsa transaction ➔ realm.commitTransaction(): Commits a transaction, all the changes made will be written to disk ➔ realm.cancelTransaction(): Cancels a transaction and all the changes will be discarded. ➔ realm.executeTransaction(): Automatically handles begin/commit, and cancel if an error happens. ➔ Eg. realm.executeTransaction(new Realm.Transaction() { @Override public void execute(Realm realm) { User user = realm.createObject(User.class); user.setName("John"); user.setEmail("john@corporation.com"); } });
• 9.
  Writes ➔ A write transactionis a transaction that is performed to update the state of your realm object ➔ All write operations (adding, modifying, and removing objects) must be wrapped in write transactions. ➔ Using write transactions, your data will always be in a consistent state. ➔ A write transaction can either be committed or cancelled. During the commit, all changes will be written to disk, and the commit will only succeed if all changes can be persisted Eg. realm.beginTransaction(); //... add or update objects here ... realm.commitTransaction();
• 10.
  Writes (cont...) ➔ Realm.executeTransaction() isa method that lets you exclude the begin() and commit() transaction steps as it handles it internally. ➔ If some Exception occurs inside a transaction, then you need to cancel that transaction in the catch block ➔ Using executeTransaction() you don’t need to call cancel transaction explicitly, it is done automatically.
• 11.
  Creating Objects ➔ RealmObjects arestrongly tied to a Realm, they should be instantiated through the Realm directly: Eg. realm.beginTransaction(); User user = realm.createObject(User.class); // Create a new object user.setName("John"); user.setEmail("john@corporation.com"); realm.commitTransaction(); ➔ It can also be created using realm.copyToRealm(). You can create an instance of an object first and add it later. Eg. User user = new User("John"); user.setEmail("john@corporation.com"); // Copy the object to Realm. Any further changes must happen on realmUser realm.beginTransaction(); User realmUser = realm.copyToRealm(user); realm.commitTransaction(); ➔ When using realm.copyToRealm(), only the returned object is managed by Realm, so any further changes should be made to returned object.
• 12.
  Auto Updating Objects RealmObjectsare live and auto-updating. Modifying objects that affect the query will be reflected in the results immediately. realm.executeTransaction(new Realm.Transaction() { @Override public void execute(Realm realm) { Dog myDog = realm.createObject(Dog.class); myDog.setName("Fido"); myDog.setAge(1); } }); Dog myDog = realm.where(Dog.class).equalTo("age", 1).findFirst(); realm.executeTransaction(new Realm.Transaction() { @Override public void execute(Realm realm) { Dog myPuppy = realm.where(Dog.class).equalTo("age", 1).findFirst(); myPuppy.setAge(2); } }); myDog.getAge(); // => 2
• 13.
  Asynchronous Transactions ➔ By usingan Asynchronous Transaction, Realm will execute that transaction on the background thread. ➔ Callbacks can be provided for successful or failure conditions. Eg. realm.executeTransactionAsync(new Realm.Transaction() { @Override public void execute(Realm bgRealm) { User user = bgRealm.createObject(User.class); user.setName("John"); user.setEmail("john@corporation.com"); } }, new Realm.Transaction.OnSuccess() { @Override public void onSuccess() { // Transaction was a success. } }, new Realm.Transaction.OnError() { @Override public void onError(Throwable error) { // Transaction failed and was automatically canceled. } });
• 14.
  Queries ➔ The following conditionsare supported: between(), greaterThan(), lessThan(), greaterThanOrEqualTo() & lessThanOrEqualTo() equalTo() & notEqualTo() contains(), beginsWith() & endsWith() isNull() & isNotNull() isEmpty() & isNotEmpty() ➔ You can also group conditions with “parentheses” to specify order of evaluation: beginGroup() is your “left parenthesis” and endGroup() your “right parenthesis”: Eg. RealmResults<User> r = realm.where(User.class) .greaterThan("age", 10) //implicit AND .beginGroup() .equalTo("name", "Peter") .or() .contains("name", "Jo") .endGroup() .findAll();
• 15.
  Aggregation Queries ➔ A RealmResultshas various aggregation methods: RealmResults<User> results = realm.where(User.class).findAll(); long sum = results.sum("age").longValue(); long min = results.min("age").longValue(); long max = results.max("age").longValue(); double average = results.average("age"); long matches = results.size(); Deletion Queries ➔ You can delete the results of a query from the Realm: RealmResults<Dog> results = realm.where(Dog.class).findAll(); // All changes to data must happen in a transaction realm.executeTransaction(new Realm.Transaction() { @Override public void execute(Realm realm) { results.removeLast(); // remove last object results.remove(5); // remove a single object Dog dog = results.get(2); results.remove(dog); } });
• 16.
  Configuring Realm ➔ Realms areequivalent of a database: they contain different kinds of objects. ➔ RealmConfiguration object is used to control all aspects of how a Realm is created. The minimal configuration usable by Realm is: RealmConfiguration config = new RealmConfiguration.Builder().build(); The above configuration will point to a file calles default.realm ➔ The RealmConfiguration can be saved as a default configuration. public class MyActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Realm realm = Realm.getDefaultInstance(); // ... Do something ... realm.close(); } }
• 17.
  In Memory Realm ➔ Todefine an instance for an un-persisted in-memory Realm: RealmConfiguration myConfig = new RealmConfiguration.Builder() .name("myrealm.realm") .inMemory() .build(); Realm.getInstance(config); Setting this will create an in-memory Realm instead of saving it to disk. In-memory Realms might still use disk space if memory is running low, but all files created by an in-memory Realm will be deleted when the Realm is closed.
• 18.
  DEMO ➔ Github Repository:RealmBookApplication
• 19.
  ➔ Realm documentation ➔ Github Repository:Realm-Java References
• 20.
  Thank You :)