Objective-c NSString 转utf-8和gb2312

#pragma mark -
#pragma mark Encode Chinese to ISO8859-1 in URL
-(NSString *)EncodeUTF8Str:(NSString *)encodeStr{
	CFStringRef nonAlphaNumValidChars = CFSTR("![        DISCUZ_CODE_1        ]’()*+,-./:;=?@_~");        
	NSString *preprocessedString = (NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault, (CFStringRef)encodeStr, CFSTR(""), kCFStringEncodingUTF8);        
	NSString *newStr = [(NSString *)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,(CFStringRef)preprocessedString,NULL,nonAlphaNumValidChars,kCFStringEncodingUTF8) autorelease];
	[preprocessedString release];
	return newStr;        
}
#pragma mark -
#pragma mark Encode Chinese to GB2312 in URL
-(NSString *)EncodeGB2312Str:(NSString *)encodeStr{
	CFStringRef nonAlphaNumValidChars = CFSTR("![        DISCUZ_CODE_1        ]’()*+,-./:;=?@_~");        
	NSString *preprocessedString = (NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(kCFAllocatorDefault, (CFStringRef)encodeStr, CFSTR(""), kCFStringEncodingGB_18030_2000);        
	NSString *newStr = [(NSString *)CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,(CFStringRef)preprocessedString,NULL,nonAlphaNumValidChars,kCFStringEncodingGB_18030_2000) autorelease];
	[preprocessedString release];
	return newStr;        
}