OC中NSString 的常用方法

 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];

    //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];

       //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);