Swift中常见的String用法,Array高阶使用,Set集合操作

String字符串常见用法

生成字符串

创建字符串
let greeting = "Hello, world!"
let name = String("John")

连接字符串：使用加号（+）或者字符串插值（使用()）来将多个字符串连接起来。
var firstName = "John"
let lastName = "Doe"
let fullName = firstName + " " + lastName // "John Doe"
let fullName1 = firstName.append(lastName) // "My name is John Doe."
let message = "My name is \(fullName)." // "My name is John Doe."

子字符串查询,替换,插入，删除

查找子字符串
let sentence = "Swift is a powerful and intuitive programming language."
if sentence.contains("Swift") {
    // do something
}
let range = sentence.range(of: "powerful") // Optional(Range(10..<18))
var str3 = "123456"
print(str.hasPrefix("123"))
print(str.hasSuffix("456"))

替换字符串
var sentence = "Swift is a powerful and intuitive programming language."
sentence = sentence.replacingOccurrences(of: "powerful", with: "amazing")

字符串删除
// 666hello_2_3_8884
str4.remove(at: str4.firstIndex(of: "1")!)
// hello_2_3_8884
str4.removeAll { $0 == "6" }
var range = str4.index(str4.endIndex, offsetBy: -4)..<str4.index(before: str4.endIndex)
// hello_2_3_4
str4.removeSubrange(range)

字符串插入
var str = "Hello, world!"
let firstChar = str[str.startIndex] // "H"
let lastChar = str[str.index(before: str.endIndex)] // "!"
str.insert("!", at: str.endIndex) // "Hello, world!!"

字符串转数组

字符串分割
let names = "John, Jane, Jim"
let arr = names.components(separatedBy: ", ") // ["John", "Jane", "Jim"]

字符串转其他

let str = "123"
let num = Int(str) // Optional(123)
let uppercased = str.uppercased() // "123"

Array数组高阶操作

map：对给定数组每个元素，执行闭包中的映射，将映射结果放置在数组中返回。

flatMap：对给定数组的每个元素，执行闭包中的映射，对映射结果进行合并操作，然后将合并操作后的结果放置在数组中返回。

compactMap：对给定数组的每个元素，执行闭包中的映射，将非空的映射结果放置在数组中返回。

compactMap：对给定数组的每个元素，执行闭包中的映射，将非空的映射结果-键值对放置在字典中返回。

filter：对给定数组的每个元素，执行闭包中的操作，将符合条件的元素放在数组中返回。

reduce：对给定数组的每个元素，执行闭包中的操作对元素进行合并，并将合并结果返回。

var arr = [1, 2, 3, 4]
// [2, 4, 6, 8]
var arr2 = arr.map { $0 * 2 }
print(arr2)
// [2, 4]
var arr3 = arr.filter { $0 % 2 == 0 }
print(arr3)
// 10
var arr4 = arr.reduce(0) { $0 + $1 }
print(arr4)
// 10
var arr5 = arr.reduce(0, +)
print(arr5)

Set集合操作

集合创建

let setA = Set(["a","b","c"])
let setB: Set = ["a","b","c"]

增删改查

setA.contains("a")
setA.insert("c")
setA.remove("a")

集合运算

let set1 = Set([1,2,3])
let set2 = Set([1,2])

//运算判断
if set1 == set2 {

}
// 子集,超集判断
set2.isSubset(of: set1)
set1.isSuperset(of: set2)

// 并集,交集
set1.union(set2)
set1.intersection(set2)