OC中常用的字符处理

NSString *str1 = @"BeiJing";
   NSString *str2 = @"beijing";  

   //全部转为大写
   NSLog(@"%@",[str1 uppercaseString]);  

   //全部转为小写
   NSLog(@"%@",[str1 lowercaseString]);  

   //首字母大写
   NSLog(@"%@",[str1 capitalizedString]);  

   //比较两个字符串内容是否相同
   BOOL b =[str1 isEqualToString:str2];  

   //两个字符串内容比较
   //NSOrderedAscending    右边 > 左边
   //NSOrderedSame         内容相同
   //NSOrderedDescending   左边 > 右边
   NSComparisonResult result = [str1 compare:str2];
   if (result == NSOrderedAscending) {
       NSLog(@"右边 > 左边");
   }else if(result == NSOrderedSame){
       NSLog(@"内容相同");
   }else if (result == NSOrderedDescending){
       NSLog(@"左边 > 右边");
   }  

   //忽略大小写进行比较，返回值与compare一样
   result = [str1 caseInsensitiveCompare:str2];
   if (result == NSOrderedAscending) {
       NSLog(@"右边 > 左边");
   }else if(result == NSOrderedSame){
       NSLog(@"内容相同");
   }else if (result == NSOrderedDescending){
       NSLog(@"左边 > 右边");
   }  

   //判断字符串是否以指定字符串开头
   [str1 hasPrefix:@"aaa"];
   //判断字符串是否以指定字符串结尾
   [str1 hasSuffix:@"aaa"];  

   //判断字符串是否包含指定字符串，返回位置和长度
   NSRange range = [@"123456" rangeOfString:@"456"];
   NSLog(@"%@", NSStringFromRange(range));  

   //反向搜索
   range = [@"123456456qweasasd456" rangeOfString:@"456" options:NSBackwardsSearch];
   NSLog(@"%@",NSStringFromRange(range));  

   //指定范围进行搜索
   range = NSMakeRange(0, 9);
   range = [@"123456456qweasasd456" rangeOfString:@"456" options:NSBackwardsSearch range:range];
   NSLog(@"%@",NSStringFromRange(range));  

<pre name="code" class="cpp">//字符串的截取
        NSString *str = @"123456789";
        NSLog(@"%@",[str substringFromIndex:3]);
        NSLog(@"%@",[str substringToIndex:6]);
        NSLog(@"%@",[str substringWithRange:NSMakeRange(3, 3)]);  

        //用指定字符串分割字符串，返回一个数组
        NSArray *array = [@"1,2,3,4,5,6" componentsSeparatedByString:@","];
        NSLog(@"%@",array);  

        //将数组中的字符串组合成一个文件路径
        NSMutableArray *components = [NSMutableArray array];
        [components addObject:@"Users"];
        [components addObject:@"CentralPerk"];
        [components addObject:@"Desktop"];
        NSString *path = [NSString pathWithComponents:components];
        NSLog(@"%@",path);  //Users/CentralPerk/Desktop  

        //将一个路径分割成一个数组
        NSArray *array1 = [path pathComponents];
        NSLog(@"%@",array1);  

        //判断是否为绝对路径(依据：是否以‘/‘开始)
        path = @"/Users/CentralPerk/Desktop";
        NSLog(@"%i",[path isAbsolutePath]);  

        //获取最后一个目录
        NSLog(@"%@",[path lastPathComponent]);  

        //删除最后一个目录
        NSLog(@"%@",[path stringByDeletingLastPathComponent]);  

        //拼接一个目录
        NSLog(@"%@",[path stringByAppendingPathComponent:@"aaa"]);   ///Users/CentralPerk/Desktop/aaa
        NSLog(@"%@",[path stringByAppendingString:@"aaa"]);      ///Users/CentralPerk/Desktopaaa
        NSLog(@"%@",[path stringByAppendingFormat:@"%@%@",@"b",@"c"]);  ///Users/CentralPerk/Desktopbc  

        //拓展名出来
        //获取拓展名,不带.
        NSString *str2 = @"Users/CentralPerk/Desktop/test.txt";
        NSLog(@"%@",[str2 pathExtension]);
        //添加拓展名,不需要带.
        NSLog(@"%@",[str2 stringByAppendingPathExtension:@"mp3"]);
        //删除拓展名,带.一块删除
        NSLog(@"%@",[str2 stringByDeletingPathExtension]);  

        //字符串转为 int double float
        NSString *str3 = @"123";
        NSLog(@"%i",[str3 intValue]);
        NSLog(@"%zi",[str3 length]);  

        //取出指定位置的字符
        unichar c = [str3 characterAtIndex:2];
        NSLog(@"%c",c);  

        //转为C语言的字符串
        const char *s = [str3 UTF8String];
        NSLog(@"%s",s);
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