转自：http://blog.sina.com.cn/s/blog_5421851501014xif.html
去除 username中的空格，table
newline，nextline
代码如下：（三行代码）
NSCharacterSet *whitespace =
[NSCharacterSet whitespaceAndNewlineCharacterSet];
NSString
* username = [mUsernameField
stringValue];
username =
[username stringByTrimmingCharactersInSet:whitespace];
注释：
stringByTrimmingCharactersInSet:
Returns
a new string made by removing from both ends of the receiver characters
contained in a given character
set.
whitespaceAndNewlineCharacterSet
Returns
a character set containing only the whitespace characters space (U+0020) and tab
(U+0009) and the newline and nextline characters (U+000A–U+000D,
U+0085).
另外可以用 whitespaceCharacterSet 替换 whitespaceAndNewlineCharacterSet 区别newline
nextline
whitespaceCharacterSet
Returns
a character set containing only the in-line whitespace characters space (U+0020)
and tab (U+0009).
NSString *temptext = [messageTextField.text
stringByTrimmingCharactersInSet:[NSCharacterSet
whitespaceCharacterSet]];
NSString *text = [temptext
stringByTrimmingCharactersInSet:[NSCharacterSet
whitespaceAndNewlineCharacterSet ]];
第1行是去除2端的空格
第2行是去除回车