title: Swift naming conventions for booleans, constants and @IBAction selectors?
body: <p>I have been reading the <a href="https://swift.org/documentation/api-design-guidelines/" rel="noreferrer">API Design Guidelines</a> for <code>Swift</code> and some posts regarding naming those entities I said in the title of the question, but I am still not clear about that.</p>
  
  <p>I am developing in <code>Swift 3</code>.</p>
  
  <ol>
  <li>Boolean variables should be prefixed with <code>is-</code>, with <code>has-</code>, or both prefixes are appropriate?</li>
  <li>Methods returning <code>Bool</code> selectors should also be prefixed <code>is</code>/<code>has</code>?</li>
  <li>Constant variables that, for example, you define to avoid magic numbers, should start with a <code>k</code>? (for example, <code>kMaxLength</code>). I think this was a convention for <code>Objective-C</code>, is it for <code>Swift</code> as well?</li>
  <li>The name for an <code>@IBAction</code> selector, should refer to the control that triggers the action, or the task it does? (For example: <code>doneButtonTapped</code> vs <code>validateInput</code>)</li>
  </ol>