Added pageIndex as additional category item.

MSPageViewController/Source/MSPageViewController+Protected.h

@@ -9,9 +9,6 @@
 #import "MSPageViewController.h"
 
 /**
- * Subclassing notes:
- *  Child view controllers must conform to `MSPageViewControllerChild`.
- *
  * @see `MSPageViewControllerPage`.
  */
 @interface MSPageViewController () <UIPageViewControllerDataSource>
@@ -26,7 +23,7 @@
 /**
  * Can be overriden to perform additional configuration on the controller.
  */
-- (void)setUpViewController:(UIViewController<MSPageViewControllerChild> *)viewController
+- (void)setUpViewController:(UIViewController *)viewController
                     atIndex:(NSInteger)index __attribute((objc_requires_super));
 
 /**

MSPageViewController/Source/MSPageViewController.h

@@ -15,9 +15,3 @@
 @interface MSPageViewController : UIPageViewController
 
 @end
-
-@protocol MSPageViewControllerChild <NSObject>
-
-@property (nonatomic) NSInteger pageIndex;
-
-@end

MSPageViewController/Source/MSPageViewController.m

@@ -8,6 +8,7 @@
 
 #import "MSPageViewController.h"
 #import "MSPageViewController+Protected.h"
+#import "UIViewController+MSPageViewController.h"
 
 @implementation MSPageViewController
 
@@ -47,7 +48,7 @@ - (NSInteger)pageCount {
     return (NSInteger)self.pageIdentifiers.count;
 }
 
-- (void)setUpViewController:(UIViewController<MSPageViewControllerChild> *)viewController
+- (void)setUpViewController:(UIViewController *)viewController
                     atIndex:(NSInteger)index {
 
 }
@@ -72,34 +73,30 @@ - (void)viewDidLoad {
 #pragma mark - UIPageViewControllerDataSource
 
 - (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
-      viewControllerBeforeViewController:(UIViewController<MSPageViewControllerChild> *)viewController {
+      viewControllerBeforeViewController:(UIViewController *)viewController {
     const NSInteger index = viewController.pageIndex;
 
     return (index == NSNotFound) ? nil : [self viewControllerAtIndex:index - 1];
 }
 
 - (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
-       viewControllerAfterViewController:(UIViewController<MSPageViewControllerChild> *)viewController {
+       viewControllerAfterViewController:(UIViewController *)viewController {
     const NSInteger index = viewController.pageIndex;
 
     return (index == NSNotFound) ? nil : [self viewControllerAtIndex:index + 1];
 }
 
 - (UIViewController *)viewControllerAtIndex:(NSInteger)index {
-    UIViewController<MSPageViewControllerChild> *result = nil;
+    UIViewController *result = nil;
 
     if (index >= 0 && index < self.pageCount) {
         NSAssert(self.storyboard,
                  @"This controller is only meant to be used inside of a UIStoryboard");
 
         result = [self.storyboard instantiateViewControllerWithIdentifier:self.pageIdentifiers[(NSUInteger)index]];
-        
+
         NSParameterAssert(result);
-        NSAssert([result conformsToProtocol:@protocol(MSPageViewControllerChild)],
-                 @"Child view controller (%@) must conform to %@",
-                 result,
-                 NSStringFromProtocol(@protocol(MSPageViewControllerChild)));
-
+
         result.pageIndex = index;
 
         [self setUpViewController:result

MSPageViewController/Source/UIViewController+MSPageViewController.h

@@ -0,0 +1,14 @@
+//
+//  UIViewController+MSPageViewController.h
+//  MSPageViewController
+//
+//  Created by Christoph Keller on 04.12.14.
+//
+
+#import <UIKit/UIKit.h>
+
+@interface UIViewController (MSPageViewController)
+
+@property (nonatomic) NSInteger pageIndex;
+
+@end

MSPageViewController/Source/UIViewController+MSPageViewController.m

@@ -0,0 +1,24 @@
+//
+//  UIViewController+MSPageViewController.m
+//  MSPageViewController
+//
+//  Created by Christoph Keller on 04.12.14.
+//
+
+#import "UIViewController+MSPageViewController.h"
+#import <objc/runtime.h>
+
+static char kMSPageViewControllerPageIndexKey;
+
+@implementation UIViewController (MSPageViewController)
+
+- (NSInteger)pageIndex {
+    NSNumber *number = (NSNumber *)objc_getAssociatedObject(self, &kMSPageViewControllerPageIndexKey);
+    return [number integerValue];
+}
+
+- (void)setPageIndex:(NSInteger)pageIndex {
+    objc_setAssociatedObject(self, &kMSPageViewControllerPageIndexKey, @(pageIndex), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+@end

README.md

@@ -17,7 +17,6 @@ First you must create a [subclass of ```MSPageViewController```](MSPageViewContr
 
 Then you have to create a storyboard, add a ```UIPageViewController``` object and change its class to ```MSPageViewController```.
 Then you can add the controllers, setting their ```Storyboard ID```s to what you returned in ```pageIdentifiers```.
-Each of them must be a class that conforms to ```MSPageViewControllerChild``` (if you don't need to add any extra functionality to it you can use [```MSPageViewControllerPage```](MSPageViewController/Source/MSPageViewControllerPage.h)).
 
 When your controller is instantiated, it will use these controllers to create each page.