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How to perform complex queries and filters in Realm Database in Kotlin

How to perform complex queries and filters in Realm Database in Kotlin.

Here is a step-by-step tutorial on how to perform complex queries and filters in Realm Database using Kotlin:

Step 1: Set Up Realm Database​

  1. Add the Realm dependency to your project's build.gradle file:
implementation 'io.realm:realm-android:10.8.0'
  1. Initialize Realm in your application class:
class MyApp : Application() {
    override fun onCreate() {
        super.onCreate()
        Realm.init(this)
    }
}

Step 2: Define Realm Object Model​

  1. Create a Kotlin data class that represents your Realm object:
open class Person(
    @PrimaryKey
    var id: String = UUID.randomUUID().toString(),
    var name: String = "",
    var age: Int = 0,
    var email: String = ""
) : RealmObject() {}
  1. Add the @RealmClass annotation to the data class:
@RealmClass
open class Person(
    //...
) : RealmObject() {}

Step 3: Perform Basic CRUD Operations​

  1. Get a Realm instance:
val realm = Realm.getDefaultInstance()
  1. Create or update an object:
realm.executeTransaction { realm ->
    val person = Person()
    person.name = "John Doe"
    person.age = 25
    person.email = "[email protected]"
    realm.copyToRealmOrUpdate(person)
}
  1. Query all objects of a specific type:
val persons = realm.where(Person::class.java).findAll()
  1. Update an object:
realm.executeTransaction { realm ->
    val person = realm.where(Person::class.java).equalTo("id", "123").findFirst()
    person?.name = "Jane Doe"
}
  1. Delete an object:
realm.executeTransaction { realm ->
    val person = realm.where(Person::class.java).equalTo("id", "123").findFirst()
    person?.deleteFromRealm()
}

Step 4: Perform Complex Queries and Filters​

  1. Query with conditions:
val adults = realm.where(Person::class.java).greaterThan("age", 18).findAll()
  1. Query with multiple conditions:
val filteredPersons = realm.where(Person::class.java)
    .equalTo("name", "John Doe")
    .greaterThan("age", 18)
    .findAll()
  1. Query with sorting:
val sortedPersons = realm.where(Person::class.java)
    .sort("age", Sort.DESCENDING)
    .findAll()
  1. Query with case-insensitive search:
val caseInsensitiveQuery = realm.where(Person::class.java)
    .contains("name", "john", Case.INSENSITIVE)
    .findAll()
  1. Query with logical operators:
val filteredPersons = realm.where(Person::class.java)
    .beginGroup()
        .equalTo("name", "John Doe")
        .or()
        .like("email", "*@example.com")
    .endGroup()
    .findAll()
  1. Query with distinct values:
val distinctNames = realm.where(Person::class.java).distinct("name")

That's it! You now know how to perform complex queries and filters in Realm Database using Kotlin. You can use these techniques to efficiently query and filter your data based on various conditions and criteria in your Android applications.