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 = [NSStringstringWithString: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 = [NSMutableStringstringWithString: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);