[code]
//
// main.swift
// t1
//
// Created by liu qing on 15/9/13.
// Copyright (c) 2015年 liu qing. All rights reserved.
//

import Foundation

//println("Hello, World!") //output function
//Optional 可选类型
let t:Int? = 404

let p = "a"//"123"
let cn:Int? = p.toInt();

/*
1.只有可选类型可以用nil赋值 var a = nil is error
2.如果有变量或者常量需要适配不存在的情况，声明变量或者常量为可选类型
3.可选类型默认初始值为nil
*/
//var st:String? = nil
var st:String?

let hasValue = st?.hashValue //问号询问可选类型是否响应后面这个方法
println("hasValue is \(hasValue)") //output hasValue is nil

var st2:String? = "hello"
let hasValue2 = st2?.hashValue
println("hasValue2 is \(hasValue2)")

/*
使用场景：
1.声明Optional变量
2.用在Optional值操作中，用来判断是否响应后面的操作
3.ui
*/

[/code]

[code]
//
// main.swift
// t1
//
// Created by liu qing on 15/9/13.
// Copyright (c) 2015年 liu qing. All rights reserved.
//

import Foundation

//println(“Hello, World!”) //output function

var a:Int=42 //变量
let b:Double=12 //常量
//变量和常量一定要初始化
//println(b)

var π:Double = 3.14 //按键option+p输出π
var 你好 = “也行”
let =”旺旺”
//println(π)
//println(你好)
//println()

let int1 = UInt8.min
let int2 = UInt8.max
let int3 = 0o21 //8进制
let int4 = 0x11

//println(int1,b)
//类型别名
typealias cool = Int
var t1:cool = 45
t1 = 10
//println(t1)
//array
var t2 = []
var ea:Array = [Int]()
var t3 = [“1″,”b”]
t3.append(“sdf”)
t3.insert(“qwe”, atIndex:1);
println(t3[0])
//dictionay
var t4 = [:]
var t5 = Dictionary()

t5 = [“a”:”123″,”b”:”er”]

t5[“c”]=”occ 123″
println(t5);

t5[“a”] = nil
println(t5);

t5.removeValueForKey(“b”)
println(t5);

println(“count:”+String(t5.count));

for(key,value) in t5 {
println(“\(key):\(value)”)
}

for key in t5.keys{
println(key)
}

for value in t5.values{
println(value)
}

let allkeys = Array(t5.keys) //把所有的key转换成数组
let allvalues = Array(t5.values) //把所有的values转换成数组

println(allkeys,allvalues)
[/code]