[iPhone] 去除nsstring中的空格

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).