Caching ViewControllers

.gitignore

@@ -22,4 +22,7 @@ build/
 *.dep
 # Cocoapods
 Pods
-Podfile.lock
+Podfile.lock
+# AppCode specific files
+.idea/
+*.iml

MHCustomTabBarController/MHCustomTabBarController.h

@@ -24,8 +24,10 @@
 
 @interface MHCustomTabBarController : UIViewController
 
-@property(weak,nonatomic)UIViewController *currentViewController;
-@property (strong, nonatomic) NSString *currentIdentifier;
+@property(weak,nonatomic)UIViewController *destinationViewController;
+@property (strong, nonatomic) NSString *destinationIdentifier;
+@property (strong, nonatomic) NSMutableDictionary *viewControllers;
+@property (strong, nonatomic) UIViewController *oldViewController;
 @property (weak, nonatomic) IBOutlet UIView *container;
 @property (weak, nonatomic) IBOutlet UIView *buttonView;
 

MHCustomTabBarController/MHCustomTabBarController.m

@@ -29,6 +29,8 @@ - (void)viewDidLoad
 {
     [super viewDidLoad];
 	// Do any additional setup after loading the view, typically from a nib.
+
+    _viewControllers = [NSMutableDictionary dictionary];
 }
 
 -(void) viewWillAppear:(BOOL)animated
@@ -68,8 +70,7 @@ - (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInte
 
 }
 
-- (BOOL)shouldAutorotateToInterfaceOrientation:
-(UIInterfaceOrientation)interfaceOrientation {
+- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
     return YES;
 }
 
@@ -78,6 +79,13 @@ - (BOOL)shouldAutorotateToInterfaceOrientation:
 
 -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
 
+    _oldViewController = _destinationViewController;
+
+    //if view controller isn't already contained in the viewControllers-Dictionary
+    if (![[_viewControllers allKeys] containsObject:segue.identifier]) {
+        [_viewControllers setObject:segue.destinationViewController forKey:segue.identifier];
+    }
+
     for (UIView *subview in _buttonView.subviews) {
         if ([subview isKindOfClass:[UIButton class]]) {
             [((UIButton *)subview) setSelected:NO];
@@ -86,14 +94,14 @@ -(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
 
     UIButton *button = (UIButton *)sender;
     [button setSelected:YES];
-    self.currentIdentifier = segue.identifier;
-    self.currentViewController = segue.destinationViewController;
+    self.destinationIdentifier = segue.identifier;
+    self.destinationViewController = [_viewControllers objectForKey:self.destinationIdentifier];
 
 
 }
 
 - (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
-    if ([self.currentIdentifier isEqual:identifier]) {
+    if ([self.destinationIdentifier isEqual:identifier]) {
         //Dont perform segue, if visible ViewController is already the destination ViewController
         return NO;
     }
@@ -105,7 +113,7 @@ - (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sende
 
 - (void)didReceiveMemoryWarning {
     for (UIViewController *vc in self.childViewControllers) {
-        if (![vc isEqual:self.currentViewController]) {
+        if (![vc isEqual:self.destinationViewController]) {
             [vc willMoveToParentViewController:nil];
             [vc removeFromParentViewController];
         }

MHCustomTabBarController/MHTabBarSegue.m

@@ -26,15 +26,20 @@
 @implementation MHTabBarSegue
 - (void) perform {
     MHCustomTabBarController *tabBarViewController = (MHCustomTabBarController *)self.sourceViewController;
-    UIViewController *destinationViewController = (UIViewController *) self.destinationViewController;
+    UIViewController *destinationViewController = (UIViewController *) tabBarViewController.destinationViewController;
 
+    //remove old viewController
+    if (tabBarViewController.oldViewController) {
+        [tabBarViewController.oldViewController willMoveToParentViewController:nil];
+        [tabBarViewController.oldViewController.view removeFromSuperview];
+        [tabBarViewController.oldViewController removeFromParentViewController];
+    }
+
 
     destinationViewController.view.frame = tabBarViewController.container.bounds;
     [tabBarViewController addChildViewController:destinationViewController];
     [tabBarViewController.container addSubview:destinationViewController.view];
     [destinationViewController didMoveToParentViewController:tabBarViewController];
-
-    tabBarViewController.currentViewController = destinationViewController;
 }
 
 @end