Set horizontal & vertical alignment default to center. Use ivar to set layout.

Author: Rajinder Ramgarhia

AsyncDisplayKit/ASButtonNode.h

@@ -31,12 +31,12 @@ typedef enum : NSUInteger {
  */
 @property (nonatomic, assign) BOOL laysOutHorizontally;
 
-/** Horizontally align content(text or image).
+/** Horizontally align content (text or image).
  Defaults to ASAlignmentMiddle.
  */
 @property (nonatomic, assign) ASHorizontalAlignment contentHorizontalAlignment;
 
-/** Vertically align content(text or image).
+/** Vertically align content (text or image).
  Defaults to ASAlignmentCenter.
  */
 @property (nonatomic, assign) ASVerticalAlignment contentVerticalAlignment;

AsyncDisplayKit/ASButtonNode.mm

@@ -39,6 +39,9 @@ - (instancetype)init
     _titleNode = [[ASTextNode alloc] init];
     _imageNode = [[ASImageNode alloc] init];
 
+    _contentHorizontalAlignment = ASAlignmentMiddle;
+    _contentVerticalAlignment = ASAlignmentCenter;
+    
     [self addSubnode:_titleNode];
     [self addSubnode:_imageNode];
 
@@ -195,8 +198,8 @@ - (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize
   ASStackLayoutSpec *stack = [[ASStackLayoutSpec alloc] init];
   stack.direction = self.laysOutHorizontally ? ASStackLayoutDirectionHorizontal : ASStackLayoutDirectionVertical;
   stack.spacing = self.contentSpacing;
-  stack.horizontalAlignment = self.contentHorizontalAlignment ? self.contentHorizontalAlignment : ASAlignmentMiddle;
-  stack.verticalAlignment = self.contentVerticalAlignment ? self.contentVerticalAlignment  : ASAlignmentCenter;
+  stack.horizontalAlignment = _contentHorizontalAlignment;
+  stack.verticalAlignment = _contentVerticalAlignment;
 
   NSMutableArray *children = [[NSMutableArray alloc] initWithCapacity:2];
   if (self.imageNode.image) {