Change the example

RGPaperLayout/Base.lproj/Main.storyboard

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="6254" systemVersion="14C109" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" initialViewController="vXZ-lx-hvc">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="6254" systemVersion="14A389" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" initialViewController="vXZ-lx-hvc">
     <dependencies>
         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="6247"/>
         <capability name="Constraints to layout margins" minToolsVersion="6.0"/>
@@ -89,6 +89,7 @@
                                 </cells>
                                 <connections>
                                     <outlet property="dataSource" destination="vXZ-lx-hvc" id="Nhw-sW-FtM"/>
+                                    <outlet property="delegate" destination="vXZ-lx-hvc" id="enX-Ys-TKR"/>
                                 </connections>
                             </collectionView>
                         </subviews>

RGPaperLayout/ViewController.m

@@ -10,9 +10,13 @@
 #import "ViewController.h"
 #import "RGCollectionViewCell.h"
 
-@interface ViewController ()
+@interface ViewController () <UICollectionViewDelegate>
+
 @property (weak, nonatomic) IBOutlet UICollectionView *collectionView;
 @property NSMutableArray *listOfData;
+@property (nonatomic, strong) UIImageView *imageView;
+@property (nonatomic, strong) UIImageView *mainImageView;
+
 
 @end
 
@@ -23,31 +27,45 @@ - (void)viewDidLoad {
     // Do any additional setup after loading the view, typically from a nib.
     self.listOfData = [@[@"climb",@"ice",@"lake",@"shark",@"whale",@"climb",@"ice",@"lake",@"shark",@"whale",@"climb",@"ice",@"lake",@"shark",@"whale"]mutableCopy];
 
+    [self setupEffectImage:[UIImage imageNamed:@"climb"]];
+}
+
+- (void)didReceiveMemoryWarning {
+    [super didReceiveMemoryWarning];
+    // Dispose of any resources that can be recreated.
+}
+
+#pragma mark - Blur Effect Helper Method
+
+- (void)setupEffectImage:(UIImage *)effectImage {
     //---> setting up the look of the collection View + the main View
     UIVisualEffect *effect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
+
     UIVisualEffectView *effectView = [[UIVisualEffectView alloc]initWithEffect:effect];
     effectView.frame = self.collectionView.bounds;
-    UIImageView *imageView = [[UIImageView alloc]initWithFrame:self.collectionView.bounds];
-    imageView.image = [UIImage imageNamed:@"ice"];
+
+    self.imageView = [[UIImageView alloc]initWithFrame:self.collectionView.bounds];
+    self.imageView.image = effectImage;
 
     UIView *viewFrame = [[UIView alloc]initWithFrame:self.collectionView.bounds];
-    [viewFrame addSubview:imageView];
+    [viewFrame addSubview:self.imageView];
     [viewFrame addSubview:effectView];
 
     self.collectionView.backgroundView = viewFrame;
 
-
     UIVisualEffectView *mainEffectView = [[UIVisualEffectView alloc]initWithEffect:effect];
     mainEffectView.frame = self.view.bounds;
-    UIImageView *mainImageView = [[UIImageView alloc]initWithFrame:self.view.bounds];
-    mainImageView.image = [UIImage imageNamed:@"ice"];
-    UIView *mainViewFrame = [[UIView alloc]initWithFrame:self.view.bounds];
-    [mainViewFrame addSubview:mainImageView];
+
+    self.mainImageView = [[UIImageView alloc]initWithFrame:self.view.bounds];
+    self.mainImageView.image = effectImage;
+
+    UIView *mainViewFrame = [[UIView alloc] initWithFrame:self.view.bounds];
+    [mainViewFrame addSubview:self.mainImageView];
     [mainViewFrame addSubview:mainEffectView];
 
     [self.view insertSubview:mainViewFrame belowSubview:self.collectionView];
-
 }
+
 #pragma mark - UICollectionViewDataSource
 
 - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
@@ -70,17 +88,22 @@ - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
     return cell;
 }
 
+- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
+    [self selectedItemAtIndexPath:indexPath];
+}
+
+- (void)selectedItemAtIndexPath:(NSIndexPath *)indexPath {
+    NSString *nameOfImage = self.listOfData[indexPath.section];
+    self.imageView.image = [UIImage imageNamed:nameOfImage];
+    self.mainImageView.image = [UIImage imageNamed:nameOfImage];
+}
+
 - (void)configureCell:(RGCollectionViewCell *)cell
    forItemAtIndexPath:(NSIndexPath *)indexPath
 {
     NSString *nameOfImage = self.listOfData[indexPath.section];
     cell.imageView.image = [UIImage imageNamed:nameOfImage];
     cell.label.text = nameOfImage;
-
-}
-- (void)didReceiveMemoryWarning {
-    [super didReceiveMemoryWarning];
-    // Dispose of any resources that can be recreated.
 }
 
 @end