前言:4.0的好多都有改变,但是网上的更新很少.所以呢就随手写一下不多说还是直接上代码

!!!看下面的时候需要注意var和let的区别这里就不详细解释了可以自己去搜一下.

1.定义字符串

func definitionString() -> () {
    
    let name = "小龙"//变量字符串
    let m_name = "王"//常量字符串
    let m__name = ""//空的字符串
    let m___name = String()//空的字符串
    print(name,m_name,m__name,m___name);

}

2.字符串拼接

func StringJoint() -> () {
    let studentNum = "1"//学生的学号
    let studentName = "小龙"//学生的姓名
    print(studentNum+studentName)
    print("\(studentNum):\(studentName)")
    let arr = ["星","期","一"]
    //数组转字符串
    let today = arr.joined(separator: "__")//将数组中的数据通过__连接
    print(today)
    ///其他类型的转string
    let num1 = 10
    let num2 = 12
    let str1 = "\(num1)+\(num2)"
    print(str1)
    
}

3.枚举字符

func enumChar() -> () {
    //遍历
    let myStr = "my name is De Shuai Dong 🌺 我的"
    for char in myStr {
        print(char);
    }        
}

4.获取字符串中指定索引处的字符

func getStrChar() -> () {

    let s:String = "SwiftMineStudy"
    //取从开始的位置数index等于3的字符
    let sub0 = s.index(s.startIndex, offsetBy: 3)
    //取从最后的位置数第二个的字符
    let sub1 = s.index(s.endIndex, offsetBy: -2)
    //从sub0的位置开始数接下来的第二位的字符
    let sub2 = s.index(sub0, offsetBy: 2)
    //同上
    let sub3 = s.index(s.startIndex, offsetBy: 2)
    //取sub0之前的一位字符
    let sub4 = s.index(before: sub0)
    //取sub0之后的一位字符
    let sub5 = s.index(after: sub0)
    //取sub0之前的左右字符串
    let sub6 = s.prefix(upTo: sub0)
    //取sub0之后的所有字符串
    let sub7 = s.suffix(from: sub0)
    //拼接,字符需转为字符串
    //lableTest.text = String(s[sub0])+String(s[sub1])+sub6
    //反转字符串
    //lableTest.text = String(s.reversed())
    print(s[sub0],s[sub1],s[sub2],s[sub3],s[sub4],s[sub5],sub6,sub7)
    //字符串换行
    let name = """
                    qweqwe
                    qweqwe
                    sdfsdfsdf
               """
    print(name)
    //字符串是否为空
    if s.isEmpty {
        print("为空")
    }else{
        print("不为空")
    }
    //字符串区间截取
    //方法一
    let snowy = " Let it snow! "
    let nsrange = NSRange(location: 3, length: 6)
    let start = snowy.index(snowy.startIndex, offsetBy: nsrange.lowerBound)
    let end = snowy.index(snowy.startIndex, offsetBy: nsrange.upperBound)
    let substringRange = start..<end
    print(snowy[substringRange])
    //方法二
    let values = "abcdefg"
    let startSlicingIndex = values.index(values.startIndex, offsetBy: 3)
    let endSlicingIndex = values.index(values.endIndex, offsetBy: -2)
    let subvalues = values[startSlicingIndex...endSlicingIndex] // One-sided Slicing
    //        Range
    print(subvalues)
  
    //字符串前面是否有
    if values .hasPrefix("a") {
        print("有")
    }else{
        print("无")
    }
    //字符串后面是否有
    if values.hasSuffix("a") {
        print("有")
    }else{
        print("没有")
    }

}

5.字符串的其他用法

func 字符串的其他用法() -> () {
    //注意这里是变量
    var str:String = "av,1,2,3,4,5,6,7,8,a,b,c,d,e"
    //获取字符串长度
    print(str.count)
    if str.count>3 {
        print("长度大了")
    }
    //去除字符串中的特殊字符 只能去除一个
    str.remove(at: str.index(of: ",")!)
    print(str)
    //字符串转数组
    let arr = str.components(separatedBy: ",")
    print(arr)
    //转大写
    let str1 = str.uppercased()
    print(str1)
    //转小写
    let str2 = str.lowercased()
    print(str2)
    //每个单词首字母大写
    let str3 = str.capitalized
    print(str3)
    //字符串替换
    let str4 = str.replacingOccurrences(of: ",", with: "")
    print(str4)
    //判断是否包含某个字符串
    if str.range(of: "av") != nil {
        print("包含")
    }
    if str == str3 {
        print("相等")
    }else{
        print("不相等")
    }
    //转int
    let str5 = "123"
    let intNum:Int = Int(str5)!
    print(intNum + 3)
    
    
}

有用的话点个赞👍