Dictionarys

    var dictionary = [1:"A",2:"B",3:"C"]

• 字典存储的数据是键和值的数据对
• 键和值可以是任意数据类型
• 一个字典只能存储一种键和值的数据类型搭配

字典的意义在于可以通过键直接访问值，速度快。字典是无序的。

Dictionary Type

• Dictionary<Int , String>
• Dictionary<String , String>
  ......
• [Int:String]
• [String:String]
  ......

字典的声明

//字典的声明
var course = [1:"Java Programing",2:"C++",3:"Swift"]
var website = ["Search":"Baidu","Learn":"iMooc","News":"NetEase"]
var course1 : Dictionary<Int,String> = [1:"Java Programing",2:"C++",3:"Swift"]
var website1 : [String:String] = ["Search":"Baidu","Learn":"iMooc","News":"NetEase"]

//空字典的声明
var empty = Dictionary<Int,String>()
var empty1 = [String:String]()

当访问字典中得数据时，返回的是optional（可选型）数据,例如：

var strStr = "I want to learn" + course1[3]!//这样写才能拼接字符串

for-in循环

for (key,value) in course1{
    println("\(key):\(value)")
}