title: What's Objective-C's equivalent of Swift's inout Parameters?
body: <p>I'm back on writing Objective-C code again and is trying to find the equivalent of Swift's <code>inout</code> parameter notation in Objective-C.  </p>
  
  <pre><code>func swapTwoInts(_ a: inout Int, _ b: inout Int) {
      let temporaryA = a
      a = b
      b = temporaryA
  }
  </code></pre>
  
  <p><a href="https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html#//apple_ref/doc/uid/TP40014097-CH10-ID158" rel="noreferrer">https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html#//apple_ref/doc/uid/TP40014097-CH10-ID158</a></p>
  
  <p>So far I've learned: 1.inout is not objc-compatible. 2.objc simply doesn't have language feature like this.  </p>
  
  <p>However, when I'm designing my API, I want it to be clear that this method is modifying its parameter. Is there any good way to accomplish this in Objective-C? Thank you! </p>