object 去掉尾部符号

gistfile1.txt

    NSString * str = @"今天你还，好吗@？￥＃￥";
//    NSString *nStr = @"~`!@#$%^&*;:\"',.?";
    NSMutableCharacterSet *set = [[NSMutableCharacterSet alloc] init];
   [set formUnionWithCharacterSet:[NSCharacterSet lowercaseLetterCharacterSet]];//小写字母
    NSLog(@"1 %@",[str stringByTrimmingCharactersInSet:set]);
   [set formUnionWithCharacterSet:[NSCharacterSet uppercaseLetterCharacterSet]];//大写字母
    NSLog(@"2 %@",[str stringByTrimmingCharactersInSet:set]);
   [set formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];//符号
     NSLog(@"3 %@",[str stringByTrimmingCharactersInSet:set]);
    [set formUnionWithCharacterSet:[NSCharacterSet punctuationCharacterSet]];//标点
    NSLog(@"4 %@",[str stringByTrimmingCharactersInSet:set]);