NSCharacterSet 最常用的用法

 NSString *str = @"<p>讨厌的</p>节点<br/></pN>";
    //除去字符串中的不想要的        //invertedSet  将去除的反过来变成不去除的
    NSCharacterSet  *characterSet = [[NSCharacterSet characterSetWithCharactersInString:@"<p/brh>"] invertedSet];
    NSString *filtered = [[str componentsSeparatedByCharactersInSet:characterSet] componentsJoinedByString:@""];
    //去除两端的空格
    NSString *newString = [filtered stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    NSLog(@"%@",newString);