[Swift 官方教程]04 集合类型

Swift官方文档同步的中文快速入门教程

建议: 这部分没什么难点, 了解下各个类型的操作就行

集合的可变性 (Mutability of Collections)

是否可变取决于是 var 还是 let

数组 (Arrays)

同一类型值的顺序集合

数组类型简记法 (Array Type Shorthand Syntax)

数组的完整写法为: Array<Element>, 但通常简写为: [Element]

创建空数组 (Creating an Empty Array)

var a: [Int] = []
a.append(3)
a = []

创建有默认值的数组 (Creating an Array with a Default Value)

具有 3 个相同值的数组:

var a = Array(repeating: 0.0, count: 3)

合并两个数组 (Creating an Array by Adding Two Arrays Together)

var a = Array(repeating: 0.0, count: 3)
var b = Array(repeating: 2.5, count: 4)
var c = a + b

通过数组字面量创建数组 (Creating an Array with an Array Literal)

var a: [String] = ["Eggs", "Milk"]

访问和修改数组 (Accessing and Modifying an Array)

var a = [1, 2, 3, 4, 5]

🕐 获取的元素个数:

a.count

🕑 判断数组是否为空:

a.isEmpty

🕒 在"数组"末尾添加元素:

a.append(6)

🕓 通过索引获取和修改数组:

let e = array[0]
array[0] = "root"
array[4...6] = ["a", "b"]

🕔 插入或移除指定位置的元素:

a.insert(88, at: 0)
a.remove(at: 1)

🕕 弹出最后一位元素:

let p = a.removeLast()

遍历数组 (Iterating Over an Array)

🕐 遍历数组中的元素:

for v in array {
}

🕑 遍历数组的索引和元素:

for (i, v) in array.enumerated() {
}

集合 (Sets)

同一类型的唯一值的无序集合

集合的哈希值 (Hash Values for Set Types)

集合类型必须是可哈希的, 因为要进行值比较

集合类型语法 (Set Type Syntax)

集合类型写作: Set<Element>

创建和初始化空集合 (Creating and Initializing an Empty Set)

var s = Set<Character>()
s.insert("a")
s = []

通过数组字面量创建集合 (Creating a Set with an Array Literal)

var s: Set<String> = ["Rock", "Classical", "Hip hop"]

可以简写为:

var s: Set = ["Rock", "Classical", "Hip hop"]

访问和修改集合 (Accessing and Modifying a Set)

🕐 获取个数:

s.count

🕑 判断否为空:

s.isEmpty

🕒 插入元素:

s.insert("a")

🕓 移除元素:

s.remove("a")

🕓 是否包含某元素:

s.contains("a")

遍历集合 (Iterating Over a Set)

🕐 遍历集合元素:

for i in s {
}

🕑 排序后遍历:

for i in s.sorted() {
}

执行集合操作 (Performing Set Operations)

数学中的集合操作

基础集合操作 (Fundamental Set Operations)

![[Pasted image 20240107203713.png|550]]

集合的成员资格和等价性 (Set Membership and Equality)

let a: Set = ["🐶", "🐱"]
let b: Set = ["🐮", "🐔", "🐑", "🐶", "🐱"]
let c: Set = ["🐦", "🐭"]

🕐 判断集合是否相等:

a == b

🕑 集合操作:

a.isSubset(of: b) // 子集
a.isStrictSubset(of: b) // 严格子集
b.isSuperset(of: a) // 超集
b.isDisjoint(with: c) // 无交集

字典 (Dictionaries)

无序的, key 类型相同, value 类型相同

字典类型简记法 (Dictionary Type Shorthand Syntax)

字典定义为: Dictionary<Key, Value>, 可以简写为: [Key: Value]

创建空字典 (Creating an Empty Dictionary)

var d: [Int: String] = [:]

🕐 赋值:

d[16] = "sixteen"

通过字典字面量创建字典 (Creating a Dictionary with a Dictionary Literal)

var d: [String: Int] = ["a": 18, "b": 28]

🕐 可以简写为:

var d = ["a": 18, "b": 28]

访问和修改字典 (Accessing and Modifying a Dictionary)

🕐 获取元素个数,

d.count

🕑 判断是否为空:

d.isEmpty

🕒 通过 key 添加或修改 value:

d["c"] = 19

🕓 更新并返回旧 value (可选类型):

var d  = ["a": 18, "b": 28]
if let v = d.updateValue(19, forKey: "a") {
    print(v)
}

🕔 获取 value (可选类型):

var d  = ["a": 18, "b": 28]
if let v = d["b"] {
    print(v)
}

🕕 通过赋值方式删除元素:

dict[key] = nil

🕖 通过 key 删除并返回对应的 value (可选类型):

var d  = ["a": 18, "b": 28]
if let v = d.removeValue(forKey: "a") {
    print(v)
}

遍历字典 (Iterating Over a Dictionary)

🕐 遍历 key 和 value:

var d  = ["a": 18, "b": 28]
for (k, v) in d {
}

🕑 遍历 key :

for k in d.keys {
}

🕒 遍历 value:

for v in d.values {
}

🕓 将 key 或 value 转换为数组:

var d  = ["a": 18, "b": 28]
let a = [String](d.keys)
let b = [Int](d.values)

🕔 原地排序 key:

d.keys.sorted()

🕕 原地排序 value:

d.values.sorted()