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Swift - 字符串（String）用法详解

2020-06-04 Swift 前端之家

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下面对String常用的属性和方法做个总结

1，判断是否为空：isEmpty

 
        var 
        str: 
        String 
        = 
        "" 
       
        if 
        str.isEmpty{ 
       
        print( 
        "is empty" 
        ) 
       
        }

2，获取字符数量： string.characters.count

 
     let str = 
        "hangge.com""\(str.characters.count)个字符" 
        )

3，检查字符串是否有特定前缀/后缀： hasPrefix/hasSuffix

 
  str =str.hasSuffix(".com"){4，还可以用“\()”在字符串里包裹变量，常量 
  
       let name =let msg ="欢迎来到 \(name)"

5，大小写转换： 通过字符串的uppercaseString、lowercaseString、capitalizedString属性来访问一个字符串的大写/小写/首字母大写

 
         let str = 
         "Welecome to hangge.com" 
        
let uppercase = str.uppercaseString 
         //WELECOME TO HANGGE.COM 
        
let lowercase = str.lowercaseString 
         //welecome to hangge.com 
        
let capitalized = str.capitalizedString 
         //Welecome To Hangge.Com

6，字符串截取 （1）将String转化为NSString再截取

letstr ="Welecome to hangge.com" 
         
fromStr = (str 
        as 
        NSString 
        ).substringFromIndex(5) 
        //ome to hangge.com 
       
toStr = (str 
        ).substringToIndex(5) 
        //Welec 
       
rangeStr = (str 
        ).substringWithRange( 
        NSMakeRange 
        (4,1)) 
        //c

（2）直接调用String的对应方法（推荐）

index = str.startIndex.advancedBy(5) 
       
index2 = str.endIndex.advancedBy(-5) 
       
range = 
        Range 
        < 
        String 
        . 
        Index 
        >(start: index,end: index2) 
       
fromStr = str.substringFromIndex(index) 
        //ome to hangge.com 
       
toStr = str.substringToIndex(index2) 
        //Welecome to hangg 
       
rangeStr = str.substringWithRange(range) 
        //ome to hangg