Fix disappearing of social app example divider

UITableViewCell traverses through all its descendant views and adjusts their background color accordingly either to [UIColor clearColor], although potentially it could use the same color as the selection highlight itself. After selection, the same trick is performed again in reverse, putting all the backgrounds back as they used to be. But in our case, we don't want to have the background color disappearing so we reset it after highlighting or selection is done.

examples/SocialAppLayout/Sample/PostNode.m

@@ -15,6 +15,8 @@
 #import "LikesNode.h"
 #import "CommentsNode.h"
 
+#define PostNodeDividerColor [UIColor lightGrayColor]
+
 @interface PostNode() <ASNetworkImageNodeDelegate, ASTextNodeDelegate>
 
 @property (strong, nonatomic) Post *post;
@@ -34,6 +36,8 @@
 
 @implementation PostNode
 
+#pragma mark - Lifecycle
+
 - (instancetype)initWithPost:(Post *)post
 {
     self = [super init];
@@ -149,7 +153,7 @@
         
         // Hairline cell separator
         _divider = [[ASDisplayNode alloc] init];
-        _divider.backgroundColor = [UIColor lightGrayColor];
+        [self updateDividerColor];
         [self addSubnode:_divider];
         
         // Via
@@ -173,6 +177,20 @@
     return self;
 }
 
+- (void)updateDividerColor
+{
+    /*
+     * UITableViewCell traverses through all its descendant views and adjusts their background color accordingly
+     * either to [UIColor clearColor], although potentially it could use the same color as the selection highlight itself.
+     * After selection, the same trick is performed again in reverse, putting all the backgrounds back as they used to be.
+     * But in our case, we don't want to have the background color disappearing so we reset it after highlighting or
+     * selection is done.
+     */
+    _divider.backgroundColor = PostNodeDividerColor;
+}
+
+#pragma mark - ASDisplayNode
+
 - (void)didLoad
 {
     // enable highlighting now that self.layer has loaded -- see ASHighlightOverlayLayer.h
@@ -245,7 +263,23 @@
     _divider.frame = CGRectMake(0.0f, 0.0f, self.calculatedSize.width, pixelHeight);
 }
 
-#pragma mark - ASTextNodeDelegate methods.
+#pragma mark - ASCellNode
+
+- (void)setHighlighted:(BOOL)highlighted
+{
+    [super setHighlighted:highlighted];
+    
+    [self updateDividerColor];
+}
+
+- (void)setSelected:(BOOL)selected
+{
+    [super setSelected:selected];
+    
+    [self updateDividerColor];
+}
+
+#pragma mark - <ASTextNodeDelegate>
 
 - (BOOL)textNode:(ASTextNode *)richTextNode shouldHighlightLinkAttribute:(NSString *)attribute value:(id)value atPoint:(CGPoint)point
 {