Android Realm Starter Code

 This is MainViewModel.kt

package com.example.first

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.example.first.models.Address
import com.example.first.models.Course
import com.example.first.models.Teacher
import io.realm.kotlin.ext.query
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.stateIn
import kotlinx.coroutines.launch

class MainViewModel: ViewModel() {

    private val realm = MyApp.realm

    val courses = realm
        .query<Course>(

        )
        .asFlow()
        .map { results ->
            results.list.toList()
        }
        .stateIn(
            viewModelScope,
            SharingStarted.WhileSubscribed(),
            emptyList()
        )
    var courseDetails: Course? by mutableStateOf(null)
        private set

    fun showCourseDetails(course: Course) {
        courseDetails = course
    }
    fun hideCourseDetails() {
        courseDetails = null
    }
    fun deleteCourse() {
        viewModelScope.launch {
            realm.write {
                val course = courseDetails ?: return@write
                val latestCourse = findLatest(course) ?: return@write
                delete(latestCourse)
                courseDetails = null
            }
        }
    }
    fun addNewCourse(courseName: String, teacherFullName: String, teacherStreet: String, teacherHouseNumber: Int, teacherZip: Int, teacherCity: String) {
        viewModelScope.launch {
            realm.write {
                val address = Address().apply {
                    fullName = teacherFullName
                    street = teacherStreet
                    houseNumber = teacherHouseNumber
                    zip = teacherZip
                    city = teacherCity
                }
                val teacher = Teacher().apply {
                    this.address = address
                }
                val course = Course().apply {
                    name = courseName
                    this.teacher = teacher
                }
                copyToRealm(course)
            }
        }
    }

//    init {
//        createSampleEntries()
//    }
//    private fun createSampleEntries(){
//        viewModelScope.launch {
//             realm.write {
//                val address1= Address().apply{
//                    fullName= "John Doe"
//                    street = " John Doe Street"
//                    houseNumber = 25
//                    zip = 12345
//                    city = "Johncity"
//                }
//                val address2= Address().apply{
//                    fullName= "Jane Doe"
//                    street = " Jane Doe Street"
//                    houseNumber = 25
//                    zip = 12345
//                    city = "Johncity"
//                }
//                val course1 = Course().apply {
//                    name = "Kotlin Programming"
//                }
//                val course2 = Course().apply {
//                    name = "Android Basics"
//                }
//                val course3 = Course().apply {
//                    name = "Asynchronous Programming"
//                }
//                val teacher1 = Teacher().apply {
//                    address = address1
//                    courses = realmListOf(course1, course2)
//                }
//                val teacher2 = Teacher().apply {
//                    address = address2
//                    courses = realmListOf(course3)
//                }
//
//                course1.teacher = teacher1
//                course2.teacher = teacher1
//                course3.teacher = teacher2
//
//                address1.teacher = teacher1
//                address2.teacher = teacher2
//
//                val student1 = Student().apply {
//                    name = "John Doe"
//                }
//                val student2 = Student().apply {
//                    name = "Jane Doe"
//                }
//
//                course1.enrolledStudents.add(student1)
//                course2.enrolledStudents.add(student2)
//                course3.enrolledStudents.addAll(listOf(student1,student2))
//
//                copyToRealm(teacher1, updatePolicy = UpdatePolicy.ALL)
//                copyToRealm(teacher2, updatePolicy = UpdatePolicy.ALL)
//
//                copyToRealm(course1, updatePolicy = UpdatePolicy.ALL)
//                copyToRealm(course2, updatePolicy = UpdatePolicy.ALL)
//                copyToRealm(course3, updatePolicy = UpdatePolicy.ALL)
//
//                copyToRealm(student1, updatePolicy = UpdatePolicy.ALL)
//                copyToRealm(student2, updatePolicy = UpdatePolicy.ALL)
//
//            }
//        }
//    }

}

This is  Realm Initializer MyApp.kt

package com.example.first

import android.app.Application
import com.example.first.models.Address
import com.example.first.models.Course
import com.example.first.models.Student
import com.example.first.models.Teacher
import io.realm.kotlin.Realm
import io.realm.kotlin.RealmConfiguration

class MyApp:Application() {
    companion object {
        lateinit var realm: Realm
    }

    override fun onCreate() {
        super.onCreate()
        realm = Realm.open(
            configuration = RealmConfiguration.create(
                schema = setOf(
                    Address::class,
                    Teacher::class,
                    Course::class,
                    Student::class
                )
            )
        )
    }

}

And also Add the MyApp.kt file

package com.example.first

import android.app.Application
import com.example.first.ExpenseModels.Category
import com.example.first.ExpenseModels.Expense
import io.realm.kotlin.Realm
import io.realm.kotlin.RealmConfiguration

class ExpenseApp: Application() {
    companion object {
        lateinit var realm: Realm
    }

    override fun onCreate() {
        super.onCreate()
        realm = Realm.open(
            configuration = RealmConfiguration.create(
                schema = setOf(
                    Category::class,
                    Expense::class
                )
            )
        )
    }

}

In AndroidManifest.xml file as

<application
    android:name=".ExpenseApp"