edit ServicesFactory

app/src/main/java/it/unisannio/ding/ids/wedroid/app/util/ServicesFactory.kt

@@ -5,9 +5,10 @@ import okhttp3.OkHttpClient
 import retrofit2.Retrofit
 import retrofit2.converter.gson.GsonConverterFactory
 
-object ServicesFactory {
+class ServicesFactory private constructor(
+    reader: PreferenceReader
+) {
     private val retrofit: Retrofit
-    private lateinit var reader: PreferenceReader //TODO
 
     init {
         val httpClient = OkHttpClient.Builder()
@@ -55,5 +56,23 @@ object ServicesFactory {
     val userService by lazy {
         retrofit.create(UserService::class.java)
     }
+
+    companion object {
+        @Volatile
+        private var INSTANCE: ServicesFactory? = null
+
+        fun getInstance(reader: PreferenceReader): ServicesFactory {
+            val tempInstance = INSTANCE
+
+            if (tempInstance != null)
+                return tempInstance
+
+            synchronized(this) {
+                val instance = ServicesFactory(reader)
+                INSTANCE = instance
+                return instance
+            }
+        }
+    }
 }