Printing level tree order in objective c

gistfile1.m

//
//  Tree.h
//  learnObjectiveC
//
//  Created by kmd on 3/3/15.
//  Copyright (c) 2015 Happy Days. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface TNode : NSObject
{
}
@property (nonatomic, strong) TNode *rlink;
@property (nonatomic, strong) TNode *llink;
@property (nonatomic, assign) NSInteger data;
@end

@interface Tree : NSObject
-(TNode*) insertNode:(NSInteger) value withRootNode:(TNode*) node;
-(void) displayTree:(TNode*) rootNode;
-(void) printLevelTree:(TNode*) node;
@end

//
//  Tree.m
//  learnObjectiveC
//
//  Created by kmd on 3/3/15.
//  Copyright (c) 2015 Happy Days. All rights reserved.
//

#import "Tree.h"
#import "RRQueue.h"
@implementation TNode
@end

@implementation Tree
-(TNode*) insertNode:(NSInteger) value withRootNode:(TNode*) node{
    if (node == nil) {
        node = [TNode new];
        node.rlink = nil;
        node.llink = nil;
        node.data = value;
        return node;
    } else {
        if (value >= node.data) {
            node.rlink = [self insertNode:value withRootNode:node.rlink];
        } else {
            node.llink = [self insertNode:value withRootNode:node.llink];
        }
        return node;
    }
}
-(void) displayTree:(TNode*) rootNode {
    if (rootNode!=nil) {
        [self displayTree:rootNode.llink];
        NSLog(@"%lu", rootNode.data);
        [self displayTree:rootNode.rlink];
    }
}
-(void)printLevelTree:(TNode *)node {
    if (node == nil) {
        NSLog(@"empty tree to print");
    } else {
        // need to print it one by one using a queue
        RRQueue *q = [[RRQueue alloc] init];
        TNode *tempNode = node;
        while (tempNode != nil) {
            NSLog(@"%ld", (long)tempNode.data);
            if (tempNode.llink != nil) {
                [q enQueue:tempNode.llink];
            }
            if (tempNode.rlink != nil) {
                [q enQueue:tempNode.rlink];
            }
            tempNode = (TNode*)[q deQueue];
        }
    }
}
-(BOOL) isBinarySearchTree:(TNode*)node {
    if (node == nil) {
        return YES;
    }
    if (node.llink != nil && (node.llink.data > node.data ? YES : NO)) {
        return false;
    }
    if (node.rlink != nil && (node.rlink.data < node.data ? YES : NO)) {
        return false;
    }
    if (![self isBinarySearchTree:node.llink] || ![self isBinarySearchTree:node.rlink]) {
        return NO;
    }
    return YES;
}
@end