Nsstring的增删改查

     NSString *str1 = @"This is string A" ;
    NSString *str2 = @"This is string b" ;
    NSString *res;
    NSComparisonResult compareResult; // 声明保存字符串比较操作的结果
   
    NSLog ( @"Length of str1: %lu" ,( unsignedlong )[str1 length ]); // 字符串的长度检测方法
   
    res = [ NSString stringWithString :str1]; // 引用字符串
   
    NSLog ( @"copy : %@" , res);
   
    str2 = [str1 stringByAppendingString :str2]; // 连接字符串的方法
    NSLog ( @"Concatentation:%@" , str2);
   
    if ([str1 isEqualToString :res] == YES ) {
        NSLog ( @"str1 == res " );
    } else
        NSLog ( @"str1 != res" );
   
    compareResult = [str1 compare :str2];
   
    if (compareResult == NSOrderedAscending ) {
        NSLog ( @"str1 < str2" );
    } elseif (compareResult == NSOrderedSame )
        NSLog ( @"str1 == str2" );
    else //NsorderedDescending 大于
        NSLog ( @"str1 > str2" );
   
    res = [str1 uppercaseString ]; // 转字符串为大写
    NSLog ( @"Uppercase conversion: %s" ,[res UTF8String ]);
   
    res = [str1 lowercaseString ]; // 转字符串为小写，并未改变原本的字符串
   
    NSLog ( @"lowercase conversion:%@" ,res);
   
    NSLog ( @"Original string : %@" ,str1);

例子2


     NSString *str1 = @"This is string A" ;
    NSString *str2 = @"This is string B" ;
    NSString *res;
    NSRange subRange; // 注意不是对象变量，是结构变量
   
    res = [str1 substringToIndex : 3 ]; //substringToIndex 索引数是 0 开始，所以提取的是字符 0 ， 1 ， 2 ，如果索引数无效，会获得 Range( 范围 ) or index out of bounds 的出错信息
    NSLog ( @"First 3 chars of str1:%@" ,res);
   
    res = [str1 substringFromIndex : 5 ]; // 输出从索引字符开始到字符串结尾
    NSLog ( @"Chars from index 5 of str1 :%@" , res);
   
    res = [[str1 substringFromIndex : 8 ] substringToIndex : 6 ]; // 复合用法
    NSLog ( @"Chars from index 8 throughe 13 :%@" , res);
   
    res = [str1 substringWithRange : NSMakeRange ( 8 , 6 )]; // 接受范围函数
    NSLog ( @"Chars from index 8 throughe 13 :%@ " , res);
   
    subRange = [str1 rangeOfString : @"string A" ]; // 在一个字符串中查找另一个字符串的方法
    NSLog ( @"string is at  index %lu, length is %lu" , ( unsigned long )subRange. location ,( unsigned long )subRange. length );
   
    subRange = [str1 rangeOfString : @"string B" ];
   
    if (subRange. location == NSNotFound )
        NSLog ( @"string not found" );
    else
         NSLog ( @"String is at index %lu, length is %lu" , ( unsigned long )subRange. location , ( unsigned 
long )subRange. length );
例子3

     NSString *str1 = @"This is string A" ;
    NSString *search, *replace;
    NSMutableString *mstr;
    NSRange substr;
   
    mstr = [ NSMutableString stringWithString :str1 ];
    NSLog ( @"%@" ,mstr);
   
    [mstr insertString : @" mutable" atIndex : 7 ]; // 指定位置插入字符
    NSLog ( @"%@" ,mstr);
   
    [mstr insertString : @" and string B" atIndex : mstr. length ]; // 配合 .length 方法在末尾插入字符
    NSLog ( @"%@" ,mstr);
   
    [mstr appendString : @" and string C" ];// 简化的上一条操作
    NSLog ( @"%@" ,mstr);
   
    [mstr deleteCharactersInRange : NSMakeRange ( 16 , 13 )];// 从索引数 16 （字符串第 17 个字符）开始删除 13 个字符
    NSLog ( @"%@ 删除后 " ,mstr);
   
    substr = [mstr rangeOfString : @"string B and" ];
   
    if (substr. location != NSNotFound ) {
        [mstr deleteCharactersInRange : substr];
        NSLog ( @"%@" , mstr);
    }
   
   
    [mstr setString : @"This is string A" ];// 直接设置可变字符串
    NSLog ( @"%@ " , mstr);
   
    [mstr replaceCharactersInRange : NSMakeRange ( 8 , 8 ) withString : @"a mutable string " ];
    NSLog ( @"%@" ,mstr); // 范围替换字符串
   
    search = @"This is" ;
    replace = @"An example of " ;
   
    substr = [mstr rangeOfString : search];
   
    if (substr. location != NSNotFound ) {
        [mstr replaceCharactersInRange :substr withString :replace];
        NSLog ( @"%@" ,mstr);
    }
   
    search = @"a" ;
    replace = @"X" ;// 该为 ' 空 ' 可以删除字符串
   
    substr = [mstr rangeOfString : search];
   
//    while (substr.location != NSNotFound) {
//        [mstr replaceCharactersInRange:substr withString: replace];
//        substr = [mstr rangeOfString: search];
//    }
   
    [mstr replaceOccurrencesOfString :search withString :replace options : 2   range : NSMakeRange ( 0 , mstr. length )];//options:1 不区分大小写， 2 区分大小写
   
     NSLog ( @"%@" ,mstr);