Merge pull request #86 from TouchInstinct/refactor/tabbar_navigation_modifying

TabData modifying

tabbar-navigation/src/main/java/ru/touchin/roboswag/components/tabbarnavigation/BottomNavigationFragment.kt

@@ -1,6 +1,7 @@
 package ru.touchin.roboswag.components.tabbarnavigation
 
 import android.os.Bundle
+import android.os.Parcel
 import android.os.Parcelable
 import android.util.SparseArray
 import android.view.LayoutInflater
@@ -72,14 +73,41 @@ abstract class BottomNavigationFragment : Fragment() {
 
     private fun getNavigationActivity() = requireActivity() as BottomNavigationActivity
 
-    data class TabData(
+    class TabData(
             val viewControllerClass: Class<out ViewController<*, *>>,
-            val viewControllerState: Parcelable,
+            viewControllerState: Parcelable,
             /**
              * It can be useful in some cases when it is necessary to create ViewController
              * with initial state every time when tab opens.
              */
             val saveStateOnSwitching: Boolean = true
-    )
+    ) {
+
+        /**
+         * It is value as class body property instead of value as constructor parameter to specify
+         * custom getter of this field which returns copy of Parcelable every time it be called.
+         * This is necessary to avoid modifying this value if it would be a value as constructor parameter
+         * and every getting of this value would return the same instance.
+         */
+        val viewControllerState = viewControllerState
+            get() = field.copy()
+
+        operator fun component1() = viewControllerClass
+
+        operator fun component2() = viewControllerState
+
+        operator fun component3() = saveStateOnSwitching
+
+        private fun Parcelable.copy(): Parcelable {
+            val parcel = Parcel.obtain()
+            this.writeToParcel(parcel, 0)
+            parcel.setDataPosition(0)
+            val result = parcel.readParcelable<Parcelable>(Thread.currentThread().contextClassLoader)
+                    ?: throw IllegalStateException("It must not be null")
+            parcel.recycle()
+            return result
+        }
+
+    }
 
 }