reworked MotionIndependentController

Sources/MotionIndependentController.swift

@@ -29,19 +29,40 @@
 import UIKit
 
 public class MotionIndependentController: MotionController {
+    /// An initializer.
     public override init() {
         super.init()
     }
 
+    /**
+     Transitions source views to their corresponding destination view
+     within a given root view.
+     - Parameter rootView: A UIView.
+     - Parameter fromViews: An Array of UIViews.
+     - Parameter toViews: An Array of UIViews.
+     - Parameter completion: An optional callback.
+     */
     public func transition(rootView: UIView, fromViews: [UIView], toViews: [UIView], completion: ((Bool) -> Void)? = nil) {
         transitionContainer = rootView
         completionCallback = completion
 
         prepareTransition()
+        prepareContext(fromViews: fromViews, toViews: toViews)
+        prepareTransitionPairs()
+        
+        animate()
+    }
+}
+
+fileprivate extension MotionIndependentController {
+    /** 
+     Prepares the context.
+     - Parameter fromViews: An Array of UIViews.
+     - PArameter toViews: An Array of UIViews.
+     */
+    func prepareContext(fromViews: [UIView], toViews: [UIView]) {
         context.defaultCoordinateSpace = .sameParent
         context.set(fromViews: fromViews, toViews: toViews)
         processContext()
-    prepareTransitionPairs()
-    animate()
     }
 }