标签：style color 使用 io 数据 for ar cti
简单值：
1.let声明常量，var声明变量（声明的同时赋值，编译器会自动推断出类型）
var myVariable = 42
myVariable 50
let myConstant = 42
let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble:Double = 70
声明类型时在“量”后面加上“：”然后写上类型的名字。（值永远不会隐式转换，需要转换请显示转换“类型（量）”）
更简单的办法将值转换成字符串：\（量）
let apples = 3
let oranges = 5
let appleSummary = "I have \(apples) apples."
let fruitSummary = "I have \(apples + oranges) pieces of fruit"
2.“[]”创建数组和字典，key或者下标取值
var shoppingList = ["catfish","water","tulips","blue paint"]
shoppingList[1] = "bottle of water"
var occupations = ["Malcolm":"Captain","KayLee":"Mechanic"]
occupations["Jayne"] = "Public Relations"
空数组和空字典声明
let emptyArray = String[]()
let emptyDictionary = Dictionary<String,Float>()
如果类型信息可以别推断出来，你可以用[]和[:]来创建空数组和空字典，就想你声明变量或者给函数传递参数的时候一样
shoppingList = []
控制流
1.if,switch进行条件操作，for-in,for,while,do-while进行循环（包裹条件和循环变量括号可以省略，但是语句体的大括号是必须的）
let individualScores = [75,43,103,87,12]
var teamScore = 0
for score in individualScores{
if score>50{
teamScore += 3
}
else
{
teamScore += 1
}
}
if语句的条件必须是布尔值，一个可选的值可能是一个具体的值或者是nil，表示值缺失，在类型后面加上一个问号来标记这个变量的值是可选的。
var optionalString : String? = "Hello"
optionalString == nil
var optionalName:String?="John Appleseed"
var greeting = "Hello!"
if let name = optionalName{
greeting = "Hello, \(name)"
}
switch支持任意类型的数据以及各种比较操作
let vegetable = "red pepper"
switch vegetable{
case "celery":
let vegetableComment = "Add some raisins and make ants on a log."
case "cucumber","watercress":
let vegetableComment = "That would make a good tea sandwich."
case let x where x.hasSuffix("pepper"):
let vegetableComment = "Is it a spicy\(x)?"
default:
let vegetableComment = "Everything tastes good in soup."
}
使用for - in 来遍历字典，需呀两个变量来表示每个键值对
let interestingNumbers = {
"Prime":[2,3,5,7,11,13],
"Fibonacci":[1,1,2,3,5,8],
"Square":[1,4,9,16,25],
]
var largest = 0
for(kind,numbers) in interestingNumbers{
for number in numbers{
if number > largest{
largest = number
}
}
}
largest
var n = 2
while n < 100{
n = n*2
}
n
var m = 2
do{
m = m*2
}while m < 100
m
var firstForLoop = 0
for i in 0..3{
firstForLoop += i
}
firstForLoop
var secondForLoop = 0
for var i= 0;i < 3;++i{
secondForLoop += 1
}
secondForLoop(..不包含上界，...包含上界)
标签：style color 使用 io 数据 for ar cti
原文地址：http://blog.csdn.net/u010877867/article/details/38384951
