title: how to check nsuserdefaults is empty or not
body: <p>i am getting a list of items from sqlite database and place them in an array.</p>
  
  <p>i need to get this array first time my app runs.</p>
  
  <p>for this i am saving this array into NSuserdafaults.</p>
  
  <p>my code is like this</p>
  
  <pre><code>if ([[NSUserDefaults standardUserDefaults] arrayForKey:@"categories"]) {
  
          [[NSUserDefaults standardUserDefaults] setObject:appdelegate.categoriesList forKey:@"categories"];
          NSLog(@"categorylist&gt;&gt;&gt;&gt;&gt;&gt; %@",appdelegate.categoriesList);
      }
      categoriesArray = [[NSMutableArray alloc]init];
      categoriesArray = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"categories"] mutableCopy];
  </code></pre>
  
  <p>then it not entered into if condition.</p>
  
  <p>and if i try with not equal like this.</p>
  
  <pre><code>if (![[NSUserDefaults standardUserDefaults] arrayForKey:@"categories"]) {
  
          [[NSUserDefaults standardUserDefaults] setObject:appdelegate.categoriesList forKey:@"categories"];
          NSLog(@"categorylist&gt;&gt;&gt;&gt;&gt;&gt; %@",appdelegate.categoriesList);
      }
      categoriesArray = [[NSMutableArray alloc]init];
      categoriesArray = [[[NSUserDefaults standardUserDefaults] arrayForKey:@"categories"] mutableCopy];
  </code></pre>
  
  <p>then enter for every build and run.</p>
  
  <p>But i need this for first build and run i mean at installing time.</p>
  
  <p>can any one please help me.</p>
  
  <p>Thank u in advance.</p>
  
  <p>(let me add comment if any one did n't understand my question) </p>