Swift Section Three(分支和循环)

swift
swift

分支与循环

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// Playground - noun: a place where people can play

import UIKit

//Swift 第三课 分支与循环

//1.if else 与 for in 循环

let individualScores = [75, 43, 103, 87, 12]

var teamScore = 0

for score in individualScores {

if score > 50 {

teamScore += 3;

} else {

teamScore += 1;

}

}

print(teamScore)

//2.用"?"来声明可选变量

var optionalString: String? = "Hello"

print(optionalString == nil)

var optionalName: String? = "John Appleseed"

var greeting = "Hello!"

//3.用 if let 来进行快速判断可选变量是否为空

if let name = optionalName {

greeting = "Hello, \(name)"

}

//print(name) 请记住name并没有声明变量，它只在if let 作用域内有效

//4.switch用法

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."

}


//5.利用for in 快速遍历字典

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

}

}

}

print(largest)


//6.while repeat循环

var n = 2

while n < 100{

n = n * 2

}

print(n)


//var m = 2  //repeat这个语法可能被cut掉了，现在不能使用
//
//repeat{
//    
//    m = m * 2
//    
//}while m < 100
//
//print(m)

//6. for 的简便写法

var firstForLoop = 0

for i in 0..<4 {

firstForLoop += i

}

print(firstForLoop)


var secondForLoop = 0

for var i = 0; i < 4; ++i {

secondForLoop += i

}

print(secondForLoop)

源代码请前往我的github

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