字符串编码：
- (NSString *)urlEncode:(NSString *)oldString{
CFStringRef escaped = CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (__bridge CFStringRef)oldString, NULL, (CFStringRef)@"!*'();:@&=+$,/?%#[]", kCFStringEncodingUTF8);
return [NSString stringWithFormat:@"%@", escaped];
}
字符串解码：
- (NSString *)urlDecode:(NSString *)oldString{
NSMutableString *unescaped = [NSMutableString stringWithString:oldString];
[unescaped replaceOccurrencesOfString:@"+" withString:@" " options:NSLiteralSearch range:NSMakeRange(0, [unescaped length])];
return [unescaped stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
}