//NSString 转为 NSURL
NSString *webStr = @"www.baidu.com";
NSURL *webUrl = [NSURL URLWithString:webStr]; //NSURL 转为 NSString
NSString *newWebStr = [webUrl absoluteString];
//NSString 转为 NSURL
NSString *webStr = @"www.baidu.com";
NSURL *webUrl = [NSURL URLWithString:webStr]; //NSURL 转为 NSString
NSString *newWebStr = [webUrl absoluteString];