The Swift Programming Language--

Strings and Characters

The entire NSString API is available to call on any String value you create when type cast to NSString.

• Empty String
  let a: String = "" //String literal
  var b: String = String() //initializer
  b += "Hello"

  if a.isEmpty {
      //TODO
  }
  

• Strings are Value Types
  Copy/Not Reference

• Working with Characters
  let s: String = "Hello World"
  for i in s.characters {
  print(i)
  }

  let c: Character = "!"
  let cArr: [Character] = ["a", "b", "c"]
  var s: String = String(cArr)
  

• Concatenating Strings and Characters
  let a: String = "a"
  let b = "b"
  var c = a + b
  let d: Character = "!"
  var e: String = c.append(d)

• String Interpolation

   let pi: Double = 3.14
   var r: Double = 1.0
   var s: String = "Circle square is \(pi*r*r)."
  

• Character Count
  let a: String = "Hello"
  print("String a has (s.characters.count) characters.")

• String Indexes
  let a: String = "Hello World"
  a[a.startIndex] //H
  a[a.endIndex] // error
  a[a.endIndex.predecessor()] //d
  a[a.startIndex.successor()] //e

  let newIndex = advance(a.startIndex, 6)
  a[a.newIndex] // W
  
  for index in indices(a) {
      print(\(a[index]))
  }
  

• String Insert & Remove
  var hello: String = "Hello"
  hello.insert("!", atIndex: hello.endIndex) //Hello!
  hello.splice(" World".characters, atIndex: hello.endIndex.predecessor()) //Hello World!
  hello.removeAtIndex(hello.endIndex.predecessor()) //Hello World

  var range = advance(hello.endIndex, -6)..<hello.endIndex
  hello.removeRange(range) //Hello
  

• Comparing Strings
  Unicode comparison

  let a: String = "ABC"
  let b: String = "DEF"
  
  let flag: Bool = a.hasPrefix(A) //true
  let flag2: Bool = b.hasSuffix(E) //false
  

• UTF

  let a = "Hello World"
  for bit in a.utf8 {
         var b: String.UTF8View = bit
         print(b)
  }