/traverse the PWNode in inorder

gistfile1.txt

#import <Foundation/Foundation.h>

@interface PWNode : NSObject <NSCopying>

typedef void (^PWNodeEnumerateBlock)(NSString *value);

@property (nonatomic, copy) NSString *value;
@property (nonatomic, strong) PWNode *leftNode;
@property (nonatomic, strong) PWNode *rightNode;

@property (nonatomic, copy) PWNodeEnumerateBlock nodeEnumerateblock;

@end
  
@implementation PWNode
  
- (id)copyWithZone:(NSZone *)zone
{
  PWNode *node = [[PWNode alloc] init];
  node.value = self.value;
  node.leftNode = [self.leftNode copy];
  node.rightNode = [self.rightNode copy];

  return node;
}

+ (PWNode *)nodeWithValue:(NSString *)value
{
  PWNode *node = [[PWNode alloc] init];
  node.value = value;

  return node;
}

//traverse the tree in inorder
- (void)inorder:(PWNode *)node
{
  if(node != nil) {
    [self inorder:node.leftNode];
    self.nodeEnumerateblock(node.value);
    [self inorder:node.rightNode];
  }
}

- (void)enumerateNodesUsingBlock:(PWNodeEnumerateBlock)block
{
  self.nodeEnumerateblock = block;

  [self inorder:self];
}

@end

int main (int argc, const char * argv[])
{
  @autoreleasepool {
          
    PWNode *rootNode = [PWNode nodeWithValue:@"A"];
    rootNode.leftNode = [PWNode nodeWithValue:@"B"];
    rootNode.rightNode = [PWNode nodeWithValue:@"C"];
    rootNode.leftNode.leftNode = [PWNode nodeWithValue:@"D"];
    rootNode.leftNode.rightNode = [PWNode nodeWithValue:@"E"];
    rootNode.rightNode.leftNode = [PWNode nodeWithValue:@"F"];
    rootNode.rightNode.rightNode = [PWNode nodeWithValue:@"G"];

    [rootNode enumerateNodesUsingBlock:^(NSString *value) {
        NSLog(@"%@", value);
    }];
  }
}