Remove ASLayoutChild. ASLayout now has a position property defaults to (NAN, NAN).

AsyncDisplayKit/Layout/ASLayout.h

@@ -12,35 +12,45 @@
 #import <AsyncDisplayKit/ASAssert.h>
 #import <AsyncDisplayKit/ASLayoutable.h>
 
-/** Represents the computed size of a layout node, as well as the computed sizes and positions of its children. */
+extern CGPoint const CGPointNull;
+
+extern BOOL CGPointIsNull(CGPoint point);
+
+/** Represents a computed immutable layout tree. */
 @interface ASLayout : NSObject
 
 @property (nonatomic, readonly) id<ASLayoutable> layoutableObject;
 @property (nonatomic, readonly) CGSize size;
+/**
+ * Position parent (if any). Default to CGPointNull.
+ * 
+ * @discussion Before being used as a child layout, this property must be set and no longer equal CGPointNull.
+ *
+ * @discussion Unlike all other properties, this property is read-write because often by initializaion time, it has yet been determined.
+ * To enforce immutability, this property can be set once and only once.
+ *
+ */
+@property (nonatomic, readwrite) CGPoint position;
 /** 
- * Each item is of type ASLayoutChild. 
+ * Array of ASLayout children. Each child must have a valid non-null position.
  */
 @property (nonatomic, readonly) NSArray *children;
 
 + (instancetype)newWithLayoutableObject:(id<ASLayoutable>)layoutableObject
                                    size:(CGSize)size
+                               position:(CGPoint)position
                                children:(NSArray *)children;
 
 /**
- * Convenience that does not have any children.
+ * Convenience that has CGPointNull position.
+ */
++ (instancetype)newWithLayoutableObject:(id<ASLayoutable>)layoutableObject
+                                   size:(CGSize)size
+                               children:(NSArray *)children;
+
+/**
+ * Convenience that has CGPointNull position and no children.
  */
 + (instancetype)newWithLayoutableObject:(id<ASLayoutable>)layoutableObject size:(CGSize)size;
 
 @end
-
-@interface ASLayoutChild : NSObject
-
-@property (nonatomic, readonly) CGPoint position;
-@property (nonatomic, readonly) ASLayout *layout;
-
-/**
- * Designated initializer
- */
-+ (instancetype)newWithPosition:(CGPoint)position layout:(ASLayout *)layout;
-
-@end