OC中NSString 的常用方法

//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);