编程中的一个重要任务是把逻辑相关的一组值放在一起。比如，想象你的应用要保存用户的好友列表、最爱的图书、旅行地点等。通常有必要具备将这些值放在一起并在代码中传递的能力。容器类型让这些操作变得方便。
Swift有一组容器类型，首先介绍的是数组（array）。
数组是值的有序集合。数组的每个位置都用索引标记，任何值都可以在数组中出现多次。数组通常用于值的顺序很重要或者很有用的场合，但是值的顺序是否有意义并不是先决条件。
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##创建数组
创建数组有两种形式
import Cocoa
var bucketList: Array<String>
这里创建了一个名为bucketList的变量，类型是Array。大部分语法看起来应该都挺熟悉。比如，关键字var表示bucketList是变量。这意味着bucketList可变，所以我们可以修改这个数组。不可变数组同样存在，我们会在本章稍后讨论。
语法中的新东西是
还有另外一种语法
import Cocoa
var bucketList: [String]
方括号表示bucketList是Array实例，而String表示bucketList接受什么类型的值。
现在只是声明了bucketList，还没有初始化。这意味着它还没有准备好接受String类型的实例。如果你现在试着添加目标到bucketList中，会得到一个错误，说你在数组还未初始化bucketList时就添加实例。
初始化
import Cocoa
var bucketList: [String] = ["Climb Mt. Everest"]
这里用到了赋值运算符=和数组字面量语法["Climb Mt. Everest"]。数组字面量是用任意其包含的实例初始化数组的快捷语法。
类型推断
import Cocoa
var bucketList= ["Climb Mt. Everest"]
访问和修改数组
添加
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
这里用到append(_:)给bucketList添加值。append(_:)方法接受一个参数，类型可以是数组接受的任何类型，并将其变为数组的新元素。
删除
用函数remove(at:)来删除，通过索引来删除。
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
bucketList.remove(at: 2)
bucketList
获取数组元素个数
用数组的count的属性查看
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
print(bucketList.count)
用下标获取值
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
print(bucketList[0...2])
获取索引0到2三个值
用下标添加信息
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
bucketList[2] += " in Australia"
这里使用加法和赋值运算符+=来给索引2的元素增加文本
替换数组元素
import Cocoa
var bucketList = ["Climb Mt. Everest"]
bucketList.append("Fly hot air balloon to Fiji")
bucketList.append("Watch the Lord of the Rings trilogy in one day")
bucketList.append("Go on a walkabout")
bucketList.append("Scuba dive in the Great Blue Hole")
bucketList.append("Find a triple rainbow")
bucketList[0] = "Climb Mt. Kilimanjaro"
用循环从一个数组添加元素到另一个数组
import Cocoa
var bucketList = ["Climb Mt. Everest"]
var newItems = [
"Fly hot air balloon to Fiji",
"Watch the Lord of the Rings trilogy in one day",
"Go on a walkabout",
"Scuba dive in the Great Blue Hole",
"Find a triple rainbow"
]
for item in newItems {
bucketList.append(item)
}
bucketList
用加法和赋值运算符重构代码
import Cocoa
var bucketList = ["Climb Mt. Everest"]
var newItems = [
"Fly hot air balloon to Fiji",
"Watch the Lord of the Rings trilogy in one day",
"Go on a walkabout",
"Scuba dive in the Great Blue Hole",
"Find a triple rainbow"
]
bucketList += newItems
bucketList
插入新目标
import Cocoa
var bucketList = ["Climb Mt. Everest"]
var newItems = [
"Fly hot air balloon to Fiji",
"Watch the Lord of the Rings trilogy in one day",
"Go on a walkabout",
"Scuba dive in the Great Blue Hole",
"Find a triple rainbow"
]
bucketList += newItems
bucketList.insert("Toboggan across Alaska", at: 2)
insert(_:at:)函数有两个参数。第一个参数接受要添加到数组的实例。（回忆一下，这个数组接受String实例。）第二个参数接受你想添加的元素在数组中位置的索引。
数组相等
用==检查是否相等
import Cocoa
var bucketList = ["Climb Mt. Everest"]
var newItems = [
"Fly hot air balloon to Fiji",
"Watch the Lord of the Rings trilogy in one day",
"Go on a walkabout",
"Scuba dive in the Great Blue Hole",
"Find a triple rainbow"
]
bucketList += newItems
bucketList
bucketList.remove(at: 2)
print(bucketList.count)
print(bucketList[0...2])
bucketList[2] += " in Australia"
bucketList[0] = "Climb Mt. Kilimanjaro"
bucketList.insert("Toboggan across Alaska", at: 2)
bucketList
var myronsList = [
"Climb Mt. Kilimanjaro",
"Fly hot air balloon to Fiji",
"Toboggan across Alaska",
"Go on a walkabout in Australia",
"Find a triple rainbow",
"Scuba dive in the Great Blue Hole"
]
let equal = (bucketList == myronsList)
equal却被判定为假。为什么？
记住，数组是有序的。这意味着两个内容一样的数组如果顺序不同也会被认为是不相等的。在这个例子中，myronsList给"Find a triple rainbow"顺序不一样。
不可变数组
你花了很多精力来对目标清单数组进行小修小补，但是也可以创建一个不能修改的数组，也就是不可变数组（immutable array）。
let lunches = [
"Cheeseburger",
"Veggie Pizza",
"Chicken Caesar Salad",
"Black Bean Burrito",
"Falafel Wrap"
]
使用let关键字创建不可变数组。如果试图以任何方式修改数组，编译器会报错，提示你不能修改不可变数组。如果试图重新赋一个新数组给lunches，编译器会报错，提示无法给一个用let关键字创建的常量重新赋值。
