Swift 字符串

引用

字符串是值类型- 如果创建新String值，则在将String值传递给函数或方法时，或者将其赋值给常量或变量时，将复制该值.

一、字符串基础

1、字符串初始化

let emptyString = "hello world"
let anthoerEmptyString = String()
print("emptyString = \(emptyString) - anthoerEmptyString = \(anthoerEmptyString)")
//emptyString = hello world - anthoerEmptyString =

2、多行字符串文字

let quotation = """
The White Rabbit put on his spectacles.  "Where shall I begin,
please your Majesty?" he asked.
        
"Begin at the beginning," the King said gravely, "and go on
till you come to the end; then stop."
"""

3、字符串是否为空

if emptyString.isEmpty {
    print("Nothing to see here")
}

4、字符串遍历

for character in emptyString {
    print(character)
}

5、字符串的可变性

var variableString = "Horse"
variableString += " and carriage"
print("variableString = \(variableString)")
//variableString = Horse and carriage

二、访问和修改字符串

引用

//转义的特殊字符\0（空字符），\（反斜杠），\t（水平制表符），\n（换行符），\r（回车符），\"（双引号）和\'（单引号）

//String.Index它对应Character于字符串中每个值的位置,before之前，after之后

let greeting = "Guten Tag!"
print("startIndex:\(greeting[greeting.startIndex])")
//startIndex:G

let index1 = greeting.index(before: greeting.endIndex)
print("endIndex:\(greeting[index1])")
//endIndex:!

let index2 = greeting.index(after: greeting.startIndex)
print("Index1:\(greeting[index2])")
//Index1:u

let index3 = greeting.index(greeting.startIndex, offsetBy: 7)
print("index2: \(greeting[index3])")
//index2: a

1、字符串查找

let searchStr = "hello world"
guard searchStr.range(of: "world") != nil else {
    print("没有找到字符串")
    return
}

2、截取子串

let subStr = "我们一起去飞"
let subIndex = subStr.index(subStr.startIndex, offsetBy: 3)
let sub1 = subStr[subStr.startIndex..<subIndex]
print("sub1 = \(sub1)")
//sub1 = 我们一

let subIndex2 = subStr.index(subStr.startIndex, offsetBy: 3)
let sub2 = subStr[subIndex2..<subStr.endIndex]
print("sub2 = \(sub2)")
//sub2 = 起去飞

3、字符串拆分、转数组

let arrayStr = "11233244255266277"
let array = arrayStr.components(separatedBy: "2")
print("array = \(array)")
//array = ["11", "33", "44", "55", "66", "77"]

4、字符串替换

let arrayStr1 = "11233244255266277"
let comStr = arrayStr1.replacingOccurrences(of: "2", with: " ")
print("comStr = \(comStr)")
//comStr = 11 33 44 55 66 77

5、前缀、后缀、转大写、转小写、首字母大写，其他小写

let arrayStr2 = "11233244255266277"
//前缀
let a = arrayStr2.hasPrefix("11")
//后缀
let b = arrayStr2.hasSuffix("77")
print("a = \(a) - b = \(b)")
//a = true - b = true

let bitStr = "bei JING"
//转大写
print("big = \(bitStr.uppercased())")
//big = BEI JING

//转小写
print("small = \(bitStr.lowercased())")
//small = bei jing

//首字母大写，其他小写
print("small = \(bitStr.capitalized)")
//small = Bei Jing

6、编码、解码

let codeStr = "北京欢迎你"

//编码
if let codeStr1 = codeStr.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) {
    print("codeStr1 = \(codeStr1)")
    //codeStr1 = %E5%8C%97%E4%BA%AC%E6%AC%A2%E8%BF%8E%E4%BD%A0
    
    //解码
    if let codeStr2 = codeStr1.removingPercentEncoding {
        print("codeStr2 = \(codeStr2)")
        //codeStr2 = 北京欢迎你
    }
}