Revision as of 00:04, 27 January 2015

Intermediate Swift

Reference [WWDC Link]

Optional Type

var optionalNumber = Int?
//default init to nil
optionalNumber = 9

Non-optional type cannot be nil

Example

func findIndexOfArray(needle: String, array: String[]) => Int? {
  for (index, value) in enumerate(array) {
    if value == needle {
      return index
    }
  }
  return nil
}
var neighbors = ["Alex", "Anna", "Madison"]
let index = findIndexOfArray("Alex", neighbors)
if index {
  println("Found \(neighbors[index!])") // noticing the !. The ! will unwrapping the value. Must check non-nil it before unwrap.
}
//Optional binding: Check and unwrap at same time
if let indexValue = findIndexOfArray("Alex", neighbors) {
  println("Found \(neighbors[indexValue])")
}

A more complicated example