title: Difference between : and . in Objective-C
body: <p>So I am new to iOS and have been noticing that not only can you use . notation but there is : (colon). </p>
  
  <p>My question is what is the difference between these two notations? what do they mean? When are they used? Are they interchangeable? When is it best to use which?</p>
  
  <p>Thank you for any and all information on this matter.</p>
  
  <p><strong>Example:</strong></p>
  
  <pre><code>[self.layer setBorderColor:[UIColor blackColor].CGColor];
  self.layer.borderColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:0.5].CGColor;
  </code></pre>
  
  <p><strong>Edit:</strong></p>
  
  <p>I've even seen some instances where '<strong>:.</strong>' is used. What does that mean? (I don't have an example right now, if I find one I will update this post). </p>