[Swift]遍历字符串

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➤微信公众号：山青咏芝（shanqingyongzhi）
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➤原文地址：https://www.cnblogs.com/strengthen/p/9798159.html 
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Swift中无法再使用传统形式的for循环。

//传统for循环形式不适用于Swift
for（单次表达式;条件表达式;末尾循环体）{中间循环体；}

字符串遍历方法1：使用该indices属性可以访问字符串中各个字符的所有索引。

let str = "Strengthen!"
for index in str.indices {
    print("(str[index]) ", terminator: "")
}
// Prints "S t r e n g t h e n ! "

字符串遍历方法2：每个String值都有一个关联的索引类型，String.Index它对应Character于字符串中每个值的位置。要访问远离给定索引的索引，可以使用该index(_:offsetBy:)方法而不是多次调用其中一种方法。您可以使用下标语法来访问Character特定String索引。

extension String {
    //subscript函数可以检索数组中的值
    //按照索引方式读取字符
    subscript (_ i: Int) -> Character {
        //读取字符
        get {return self[index(startIndex, offsetBy: i)]}
    }
}

//方式1
let str = "Strengthen!"
for num in 0..<str.count
{
    let char:Character = str[str.index(str.startIndex,offsetBy: num)]
     print("(char) ", terminator: "")
}
//Prints "S t r e n g t h e n ! "

//方式2
for num in 0..<str.count
{
    let char:Character = str[num]
     print("(char) ", terminator: "")
}
//Prints "S t r e n g t h e n ! "

字符串遍历方法3：遍历字符串的每一个字符

let str = "Strengthen!"
for char in str.characters {
    print("(char) ", terminator: "")
}
//Prints "S t r e n g t h e n ! "

字符串遍历方法4：遍历字符串的每一个字符对应ASCII的整数值

let str = "Strengthen"
var strUnicodeScalars = Array(str.utf8)
print(strUnicodeScalars)
//Prints [83, 116, 114, 101, 110, 103, 116, 104, 101, 110]
for charNum in strUnicodeScalars 
{
    print("(charNum) ", terminator: "")
}
//Prints "83 116 114 101 110 103 116 104 101 110"

倒序遍历字符串方法1：reversed()

let str = "Strengthen!"
for char in str.reversed() {
    print("(char) ", terminator: "")
}
//Prints ! n e h t g n e r t S 

倒序遍历字符串方法2：stride函数 -返回一个任意可变步长类型值的序列。可变步长类型是可以设置偏移量的一维标量。

let str = "Strengthen!"
//from，to，by 最后一个值是 >(或<) to的值
for num in stride(from: str.count-1,to: 0,by: -1)
{
    let char:Character = str[str.index(str.startIndex,offsetBy: num)]
     print("(char) ", terminator: "")
}
//Prints "! n e h t g n e r t"

//from，through，by 最后一个值是 >=(或<=) through的值
for num in stride(from: str.count-1,through: 0,by: -1)
{
    let char:Character = str[str.index(str.startIndex,offsetBy: num)]
     print("(char) ", terminator: "")
}
//Prints "! n e h t g n e r t S "

字符串转字符数组：

let str = "I am Strengthen"
let array = str.components(separatedBy:" ")
print("(array) ", terminator: "")
//["I", "am", "Strengthen"] 

字符数组转字符串：

/*字符数组转字符串*/
let arrayStr = ["s","t","r","e","n","g","t","h","e","n","!"]

//方式1
let str1 = arrayStr.joined(separator: "")
let str2 = arrayStr.joined(separator: "-")
print("(str1) ", terminator: "")
print("(str2) ", terminator: "")
//strengthen! 
//s-t-r-e-n-g-t-h-e-n-! 

//方式2：注意与方式1比较，方式2只在首位添加"-"
let str3 = arrayStr.reduce("", {$0 + $1})
let str4 = arrayStr.reduce("-", {$0 + $1})
print("(str3) ", terminator: "")
print("(str4) ", terminator: "")
//strengthen!
//-strengthen! 

/*整数数组转字符串*/
let arrayInt = [0,1,2,3,4,5,6,7,8,9]
let dataInt = arrayInt.map(String.init)
let strInt = dataInt.joined(separator: "-")
print("(strInt) ", terminator: "")
//0-1-2-3-4-5-6-7-8-9

最强字符串解析，你想知道，我都有！！！

请点击下方链接继续深入学习！！！不可浅尝辄止！！！

[Swift]字符串根据索引获取指定字符，依据ASCII编码，实现字符和整数的快速转换

[Swift]字符串(String类、NSString类)常用操作

[Swift]扩展String类：extension String

[Swift]ASCII值的获取和转换：extension Character类和extension Int

[Swift]字符串大小写转换，同时实现本地化或设置语言环境