Swift-4-数组和字典

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

import UIKit

// 数组 字典
// 集合的可变性 赋值给var的集合是可变的mutable，赋值给let的集合是不可变的immutable
// 数组   Array<SomeType> 等价于 [SomeType]
var shoppingList : [String] = ["Eggs", "Milk"] // var shoppingList = ["Eggs", "Milk"] 自动推断类型
// 数组计数
println("the shopping list contains (shoppingList.count) items")

// 检查数组是否为空
if shoppingList.isEmpty {
    println("the shopping list is empty")
} else {
    println("the shopping list is not empty")
}

// 向数组中添加元素
shoppingList.append("Flour")
shoppingList += ["Baking Powder"]

// 访问数组中元素
var firstItem = shoppingList[0]

// 批量替换数组中元素 用于替换的数组元素个数与替换的范围不一定要相同
shoppingList[1...2] = ["Apples"]

// 插入元素
shoppingList.insert("Maple Syrup", atIndex: 0)

// 从数组中移除元素
let mapleSyrup = shoppingList.removeAtIndex(0)
shoppingList.removeRange(Range(start: 1, end: 2))
shoppingList.removeLast()

// 遍历数组
for item in shoppingList {
    println(item)
}

for (index, item) in enumerate(shoppingList) {
    println("Item (index + 1): (item)")
}

// 创建并初始化数组
var someInts = [Int]()
println("someInts is of type [Int] with (someInts.count) items")

// 创建数组时赋默认值
var thressDoubles = [Double](count: 5, repeatedValue: 0.0)

// 组合数组
var anotherDoubles = [Double](count: 3, repeatedValue: 0.1)
var eightDouble = thressDoubles + anotherDoubles

// 字典
//Dictionary<key, value>  [key  : value]
var airports: [String : String] = ["YYZ" : "Toronto Pearson", "DUB" : "Dublin"] // var airports = ["YYZ" : "Toronto Pearson", "DUB" : "Dublin"]

// 访问、修改字典
println("The airports dictionary contains (airports.count) items")

if airports.isEmpty {
    println("The airports dictionary is empty")
} else {
    println("The airports dictionary is not empty")
}

// 添加元素
airports["LHR"] = "London"
airports["LHR"] = "London Heathrow"

// 通过方法设置键值. 返回被替换的value optional
let oldValue = airports.updateValue("Dublin Airport", forKey: "DUB")

// 移除键值对
airports["DUB"] = nil
airports.removeValueForKey("DUB")

// 遍历
for (key, value) in airports {
    println("key: (key), value: (value)")
}