iOS开发Swift-集合类型

集合基本类型：数组 Array (有序)， 集合 Set (无序不重复)， 字典 Dictionary (无序键值对)

1.数组 Arrays

(1)数组的表示

Array<Element>
[Element]

(2)创建空数组

var someInts: [Int] = []
someInts.count    //数组长度

(3)带值数组

var a = Array(repeating: 0.0, count:3)    //[0.0, 0.0, 0.0]
//repeating:初始值.count:长度

(4)两数组相加创建数组

var a = Array(reapeating: 0.0, count = 3)
var b = Array(reapeating: 2.5, count = 3)
var c = a + b    //[0.0, 0.0, 0.0, 2.5, 2.5, 2.5]

(5)字面量创造数组

var List: [String] = ["Eggs", "Milk"]   //或者
var List = ["Eggs", "Milk"]

(6)访问数组

List.count    //长度(数据量)
List.isEmpty   //是否为空
List[0]    //Eggs
var egg = List[0]     //将第一个数组的值赋给egg

(7)添加

List.append("Flour")   //append()方法添加
List += ["Powder"]    //直接添加一个数据
List += ["Spread", "Cheese", "Butter"]    //直接添加多个数据
List.insert("up", at: 0)    //在第一个数据前添加"up"

(8)修改

List[0] = "Six Eggs"
List[4...6] = ["Banana", "Apple"]

(9)删除

let a = List.remove(at: 0)  //索引值为0的项被移除。a被赋值被删除的那一项的值。后边的项自动往前补
let apple = List.removeLast()   //移除最后一项，a被赋值被删除的那一项的值

(10)遍历

for item in List{  print(item)
}

同时需要索引和值时：

for (index,value) in List.enumerated(){print( "Item \( String(index + 1) ): \(value)" )
}

2.集合 Sets

(1)集合的表示

Set<Element>

(2)构造一个集合

var letters = Set<Character>()      //或
letters.insert("a")
letters = []

(3)字面量创造集合

var fav: Set<String> = ["Rock", "Class", "Hip"]    //或
var fav: Set = ["Rock", "Class", "Hip"]

(4)访问

fav.count    //长度
fav.isEmpty    //是否为空
fav.contains("Funk")  //检查是否包含"Funk"值

(5)添加

fav.insert("Jazz")

(6)删除

fav.remove("Rock")   //如果有这个值则返回这个值，如果没有则返回nil
fav.removeAll()

(7)遍历

for g in fav{print("\(g)")
}
//返回一个有序数组
for g in fav.sorted(){print("\(g)")
}

(8)集合操作

let add: Set = [1, 3, 5, 7, 9]
let even: Set = [0, 2, 4, 6, 8]
let single: Set = [2, 3, 5, 7]
add.union(even).sorted()    //[]   交集
add.intersection(even).sorted()   //[1, 9]   add不在single中的值的集合
add.symmetricDifference(single).sorted()    //[1, 2, 9]   add和single不相交的值

(9)集合关系

let h: Set = ["🐕", "🐱"]
let f: Set = ["🐕", "🐱", "🐥"]
let c: Set = ["🐦"]
//==: 全部相同
h.isSubset(of: f)  //true  h是否被f全包
f.isSuperset(of: h)   //true   f是否全包h
f.isDisjoint(with: c)  //true  f,c是否无交集
//isStrictSubset(of: ) / isStrictSuperSet(of: )    A是否是B的子集或父集且AB不相等

3.字典 Dictionary

(1)字典的表示

Dictionary<Key, Value>  或者  [Key: Value]

(2)创建空字典

var names: [Int: String] = [ : ]   //或者
names[16] = "sixteen"
names = [ : ]

(3)字典字面量创建字典

var airports: [String: String] = ["a": "1", "b": "2"]   //或者
var airports = ["a": "1", "b": "2"]

(4)访问

airports.count     //数量
airports,isEmpty    //是否为空

(5)新增

airports["c"] = "3"

(6)修改

airports["c"] = "4"

(7)更新

airports.updateValue("6", forkey: "a")
//如果forkey存在值则修改，返回修改前的值。不存在则返回nil

(8)检索键对应的值。无值则返回nil

airName = airports["a"]

(9)移除键值对

airports["a"] = nil   //或者
airports.removeValue(forkey: "a")    //存在时返回被移除的值，不存在时返回nil

(10)遍历

//1
for (airCode, airName) in airports{print("\(airCode) : \(airName)")
}
//2
for airCode in airports.keys{print("code: \(airCode)")
}
//3
let airCodes = [String](airports.keys)
let airNames = [String](airports.values)