Swift中常见的String用法,Array高阶使用,Set集合操作

Posted 2023-05-25 滴水微澜

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)

 

 

 

Swift数组的加法运算符用法：array1 += array2

var stringList1 = [String]()                                      //创建String类型空数组
var stringList2 = ["1", "3", "5", "7", "zoo", "9","zoo"]
var stringList3 :[String] = ["2", "4", "6","apple", "8", "10"]

stringList1 += stringList2                                        //把stringList2数组的所有元素添加到stringList1的末尾
print("stringList1: \(stringList1)")                              //输出stringList1
stringList1 += stringList3                                     　 //把stringList3数组的所有元素添加到stringList1的末尾
print("stringList1: \(stringList1)")                              //输出stringList1

运行结果：

stringList1: ["1", "3", "5", "7", "zoo", "9", "zoo"]
stringList1: ["1", "3", "5", "7", "zoo", "9", "zoo", "2", "4", "6", "apple", "8", "10"]

以上输出结果的元素无序排列，可使用数组的 sort() 方法或 sortInPlace() 方法排序，两者不同在于

sort()方法有返回值，返回一个新数组，而不改变原数组的值：

print("After sort: \(stringList1.sort())")
print("stringList1: \(stringList1)")

运行结果：

After sort: ["1", "10", "2", "3", "4", "5", "6", "7", "8", "9", "apple", "zoo", "zoo"]
stringList1: ["1", "3", "5", "7", "zoo", "9", "zoo", "2", "4", "6", "apple", "8", "10"]

sortInPlace()方法无返回值，会改变原数组的值：

stringList1.sortInPlace()
print("stringList1: \(stringList1)")

运行结果：

stringList1: ["1", "10", "2", "3", "4", "5", "6", "7", "8", "9", "apple", "zoo", "zoo"]

 

+=运算符只能用于数组之间，不能添加单个元素：

var str = "myString"
stringList1 += str         //此行报错：Binary operator ‘+=‘ cannot be applied to operands of type ‘[String]‘ and ‘String‘