Improve null safety

Author: ErikJhordan

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/data/remote/RemoteContract.kt

@@ -31,7 +31,7 @@ class RemoteContract {
     const val SUCCESS = "success"
     const val QUOTES = "quotes"
 
-    // I should't expose the access key but it is to didactic use
+    // I shouldn't expose the access key but it is to didactic use
     const val ACCESS_KEY_API_LAYER = "be4554e86f3a5670b287ccc40f5bead8"
     const val FORMAT_TYPE = "1"
   }

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/data/repository/CurrencyRepository.kt

@@ -53,7 +53,7 @@ class CurrencyRepository @Inject constructor(
         .observeOn(AndroidSchedulers.mainThread())
         .subscribe({ currencyList ->
           mutableLiveData.value = transform(currencyList)
-        }, { t: Throwable? -> t!!.printStackTrace() })
+        }, { t: Throwable? -> t?.printStackTrace() })
     allCompositeDisposable.add(disposable)
     return mutableLiveData
   }
@@ -77,7 +77,7 @@ class CurrencyRepository @Inject constructor(
           } else {
             throw Throwable("CurrencyRepository -> on Error occurred")
           }
-        }, { t: Throwable? -> t!!.printStackTrace() })
+        }, { t: Throwable? -> t?.printStackTrace() })
     allCompositeDisposable.add(disposable)
     return mutableLiveData
   }

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/data/repository/Repository.kt

@@ -21,7 +21,6 @@ import erikjhordanrey.android_kotlin_devises.domain.AvailableExchange
 import erikjhordanrey.android_kotlin_devises.domain.Currency
 import io.reactivex.Flowable
 
-
 interface Repository {
 
   fun getTotalCurrencies(): Flowable<Int>

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/di/AppComponent.kt

@@ -24,7 +24,4 @@ import javax.inject.Singleton
 @Singleton interface AppComponent {
 
   fun inject(currencyViewModel: CurrencyViewModel)
-
 }
-
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/di/AppModule.kt

@@ -27,5 +27,3 @@ class AppModule(private val currencyApplication: CurrencyApplication) {
   @Provides @Singleton fun provideContext(): Context = currencyApplication
 
 }
-
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/di/CurrencyApplication.kt

@@ -29,7 +29,7 @@ class CurrencyApplication : Application() {
     initializeDagger()
   }
 
-  fun initializeDagger() {
+  private fun initializeDagger() {
     appComponent = DaggerAppComponent.builder()
         .appModule(AppModule(this))
         .roomModule(RoomModule())

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/di/RemoteModule.kt

@@ -29,7 +29,6 @@ import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
 import retrofit2.converter.gson.GsonConverterFactory
 import javax.inject.Singleton
 
-
 @Module
 class RemoteModule {
 
@@ -50,12 +49,10 @@ class RemoteModule {
           .addConverterFactory(GsonConverterFactory.create(gson))
           .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
           .client(okHttpClient)
-          .build();
+          .build()
 
 
   @Provides @Singleton fun provideRemoteCurrencyService(retrofit: Retrofit): RemoteCurrencyService =
       retrofit.create(RemoteCurrencyService::class.java)
 
 }
-
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/di/RoomModule.kt

@@ -28,5 +28,3 @@ class RoomModule {
   @Provides @Singleton fun provideRoomCurrencyDataSource(context: Context) =
       RoomCurrencyDataSource.buildPersistentCurrency(context)
 }
-
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/domain/AvailableExchange.kt

@@ -19,4 +19,3 @@ package erikjhordanrey.android_kotlin_devises.domain
 import java.io.Serializable
 
 data class AvailableExchange(var availableExchangesMap: Map<String, Double>): Serializable
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/domain/Currency.kt

@@ -17,4 +17,3 @@
 package erikjhordanrey.android_kotlin_devises.domain
 
 data class Currency(var code: String, var country: String)
-

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/view/AboutFragment.kt

@@ -26,7 +26,6 @@ import android.view.ViewGroup
 import erikjhordanrey.android_kotlin_devises.R
 import kotlinx.android.synthetic.main.about_fragment.*
 
-
 class AboutFragment : Fragment() {
 
   companion object {
@@ -51,7 +50,6 @@ class AboutFragment : Fragment() {
     show_me_code.setOnClickListener { startActivityActionView(PROJECT_SOURCE_CODE) }
   }
 
-
   private fun startActivityActionView(url: String) {
     startActivity(Intent(Intent.ACTION_VIEW, Uri.parse(url)))
   }

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/view/CurrencyFragment.kt

@@ -40,11 +40,11 @@ class CurrencyFragment : Fragment() {
   }
 
   private val currencies = ArrayList<String>()
-  private var currenciesAdapter: ArrayAdapter<String>? = null
-  private var currencyFrom: String? = null
-  private var currencyTo: String? = null
+  private lateinit var currenciesAdapter: ArrayAdapter<String>
+  private lateinit var currencyFrom: String
+  private lateinit var currencyTo: String
 
-  private var currencyViewModel: CurrencyViewModel? = null
+  private lateinit var currencyViewModel: CurrencyViewModel
 
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
@@ -64,8 +64,8 @@ class CurrencyFragment : Fragment() {
 
   private fun initViewModel() {
     currencyViewModel = ViewModelProviders.of(this).get(CurrencyViewModel::class.java)
-    currencyViewModel?.let { lifecycle.addObserver(it) }
-    currencyViewModel?.initLocalCurrencies()
+    currencyViewModel.let { lifecycle.addObserver(it) }
+    currencyViewModel.initLocalCurrencies()
   }
 
   private fun initUI() {
@@ -74,12 +74,12 @@ class CurrencyFragment : Fragment() {
   }
 
   private fun populateSpinnerAdapter() {
-    currencyViewModel?.loadCurrencyList()?.observe(this, Observer { currencyList ->
-      currencyList!!.forEach {
+    currencyViewModel.loadCurrencyList()?.observe(this, Observer { currencyList ->
+      currencyList?.forEach {
         currencies.add(it.code + "  " + it.country)
       }
-      currenciesAdapter!!.setDropDownViewResource(R.layout.item_spinner);
-      currenciesAdapter!!.notifyDataSetChanged()
+      currenciesAdapter.setDropDownViewResource(R.layout.item_spinner)
+      currenciesAdapter.notifyDataSetChanged()
     })
 
   }
@@ -102,11 +102,13 @@ class CurrencyFragment : Fragment() {
     val quantity = currency_edit.text.toString()
     currencyFrom = getCurrencyCode(from_currency_spinner.selectedItem.toString())
     currencyTo = getCurrencyCode(to_currency_spinner.selectedItem.toString())
-    val currencies = currencyFrom + "," + currencyTo
+    val currencies = "$currencyFrom,$currencyTo"
 
     if (quantity.isNotEmpty() && currencyFrom != currencyTo) {
-      currencyViewModel?.getAvailableExchange(currencies)?.observe(this, Observer { availableExchange ->
-        exchange(quantity.toDouble(), availableExchange!!.availableExchangesMap)
+      currencyViewModel.getAvailableExchange(currencies)?.observe(this, Observer { availableExchange ->
+        availableExchange?.run {
+          exchange(quantity.toDouble(), availableExchangesMap)
+        }
       })
 
     } else {
@@ -133,11 +135,10 @@ class CurrencyFragment : Fragment() {
   }
 
   private fun showResult(result: String) {
-    val builder: AlertDialog.Builder
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-      builder = AlertDialog.Builder(context!!, R.style.AppCompatAlertDialogStyle)
+    val builder: AlertDialog.Builder = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+      AlertDialog.Builder(context!!, R.style.AppCompatAlertDialogStyle)
     } else {
-      builder = AlertDialog.Builder(context!!)
+      AlertDialog.Builder(context!!)
     }
 
     val setMessage = TextView(activity)

app/src/main/kotlin/erikjhordanrey/android_kotlin_devises/view/CurrencyViewModel.kt

@@ -48,15 +48,13 @@ class CurrencyViewModel : ViewModel(), LifecycleObserver {
     initializeDagger()
   }
 
-
   fun getAvailableExchange(currencies: String): LiveData<AvailableExchange>? {
     liveAvailableExchange = null
     liveAvailableExchange = MutableLiveData<AvailableExchange>()
     liveAvailableExchange = currencyRepository.getAvailableExchange(currencies)
     return liveAvailableExchange
   }
 
-
   fun loadCurrencyList(): LiveData<List<Currency>>? {
     if (liveCurrencyData == null) {
       liveCurrencyData = MutableLiveData<List<Currency>>()
@@ -115,9 +113,6 @@ class CurrencyViewModel : ViewModel(), LifecycleObserver {
     super.onCleared()
   }
 
-
   private fun initializeDagger() = CurrencyApplication.appComponent.inject(this)
 
 }
-
-