Android Permissions with RxJava

RxPermission.kt

import rx.Observable

interface RxPermission {
    val isGranted: Boolean

    fun request(): Observable<Boolean>
}

RxPermissions.kt

import android.Manifest
import android.app.Activity
import android.content.pm.PackageManager
import android.support.v4.app.ActivityCompat
import android.support.v4.content.ContextCompat
import rx.Observable
import rx.subjects.PublishSubject

class RxPermissions(private val activity: Activity) {
    private val register = mutableMapOf<Int, CompatRxPermission>()
    private var lastRequestCode = 0

    fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
        register[requestCode]?.apply {
            if (permissions.isNotEmpty()) {
                onResult(permissions, grantResults)
            }
        }
    }

    fun of(vararg permissions: String): RxPermission {
        val requestCode = ++lastRequestCode
        val permission = CompatRxPermission(activity, permissions, requestCode)
        register[requestCode] = permission
        return permission
    }

    fun ofExternalStorage() = of(Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE)

    fun ofAccessLocation() = of(Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION)

    private class CompatRxPermission(private val activity: Activity,
                                     private val permissions: Array<out String>,
                                     private val requestCode: Int) : RxPermission {
        private lateinit var request: PublishSubject<Boolean>

        override val isGranted: Boolean = permissions.all {
            ContextCompat.checkSelfPermission(activity, it) == PackageManager.PERMISSION_GRANTED
        }

        override fun request(): Observable<Boolean> = if (isGranted) {
            Observable.just(true)
        } else {
            ActivityCompat.requestPermissions(activity, permissions, requestCode)
            PublishSubject.create<Boolean>().apply { request = this }
        }

        fun onResult(permissions: Array<String>, grantResults: IntArray) {
            request.onNext(this.permissions.all { permissions.contains(it) }
                    && grantResults.all { it == PackageManager.PERMISSION_GRANTED })
            request.onCompleted()
        }
    }
}