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)
}