title: How to use computed property in a codable struct (swift)
body: <p>I've created a "codable" struct to serialize a data set and encode it to Json. Everything is working great except the computed properties don't show in the json string. How can I include computed properties during the encode phase.</p>
  
  <p>Ex:</p>
  
  <pre><code>struct SolidObject:Codable{
  
      var height:Double                      = 0
      var width:Double                       = 0
      var length:Double                      = 0
  
      var volume:Double {
          get{
              return height * width * length
          }
      }
  }
  
  var solidObject = SolidObject()
  solidObject.height = 10.2
  solidObject.width = 7.3
  solidObject.length = 5.0
  
  let jsonEncoder = JSONEncoder()
  do {
      let jsonData = try jsonEncoder.encode(solidObject)
      let jsonString = String(data: jsonData, encoding: .utf8)!
      print(jsonString)
  } catch {
      print(error)
  }
  </code></pre>
  
  <p>prints out "{"width":7.2999999999999998,"length":5,"height":10.199999999999999}"</p>
  
  <p>I am also curious about having 7.29999.. instead of 7.3 but my main question is "how can I include "volume" to this json string too"?</p>