 <p><strong>Swift is designed to take advantage of optional value's and optional unwrapping.</strong></p> <p>You <strong><em>could</em></strong> also declare the array as nil, as it will save you a very small (almost not noticable) amount of memory.</p> <p>I would go with an optional array instead of an array that represents a nil value to keep Swift's Design Patterns happy :)</p> <p>I also think </p> <pre><code>if let children = children { } </code></pre> <p>looks nicer than : </p> <pre><code>if(children != nil){ } </code></pre>