How to extract part of url - dart/flutter-CodePudding

I'm trying to extract the part of url (To be more specific, I'm trying to extract the value of page_info parameter in the url which is next to rel="next"

String testUrl = "<https://demo.myshopify.com/admin/api/2022-01/products.json?limit=10&page_info=eyJkaXJlY3Rpb24iOiJwcmV2IiwibGFzdF9pZCI6NjczMDU4MDcyMTc1NCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBCcmFjZWxldCJ9>; rel='previous', <https://demo.myshopify.com/admin/api/2022-01/products.json?limit=10&page_info=eyJkaXJlY3Rpb24iOiJuZXh0IiwibGFzdF9pZCI6NjczMDIyNzcxMjA5MCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBIZWFydCBQZW5kYW50IE5lY2tsYWNlIn0>; rel='next'";

List<String> splitUrl = testUrl.split("=");
    print(splitUrl[5]);

// this is what it prints out
eyJkaXJlY3Rpb24iOiJuZXh0IiwibGFzdF9pZCI6NjczMDIyNzcxMjA5MCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBIZWFydCBQZW5kYW50IE5lY2tsYWNlIn0>; rel

// this is what I'm trying to extract 

eyJkaXJlY3Rpb24iOiJuZXh0IiwibGFzdF9pZCI6NjczMDIyNzcxMjA5MCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBIZWFydCBQZW5kYW50IE5lY2tsYWNlIn0 

// value for rel="next"

I tried to split the url by using split function on String but that would also bring the angle bracket with it. I'm trying to extract only page_info= parameter value which is for rel="next"

I know this has to do something with regex but I'm not really good at it! Any help would be really appreciated

I grabbed that url from header response (paginated REST API), it returns two page_info parameters (one for next and other one for previous page) I'm trying to extract value for next page. Splitting the url didn't help me

thank you

CodePudding user response：

the regEx pattern page_info=([\w] ) gives you

eyJkaXJlY3Rpb24iOiJwcmV2IiwibGFzdF9pZCI6NjczMDU4MDcyMTc1NCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBCcmFjZWxldCJ9

eyJkaXJlY3Rpb24iOiJuZXh0IiwibGFzdF9pZCI6NjczMDIyNzcxMjA5MCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBIZWFydCBQZW5kYW50IE5lY2tsYWNlIn0

https://regexr.com/6qj1h

CodePudding user response：

An alternative approach is to parse the URL:

void main() {
  String testUrl = "<https://demo.myshopify.com/admin/api/2022-01/products.json?limit=10&page_info=eyJkaXJlY3Rpb24iOiJwcmV2IiwibGFzdF9pZCI6NjczMDU4MDcyMTc1NCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBCcmFjZWxldCJ9>; rel='previous', <https://demo.myshopify.com/admin/api/2022-01/products.json?limit=10&page_info=eyJkaXJlY3Rpb24iOiJuZXh0IiwibGFzdF9pZCI6NjczMDIyNzcxMjA5MCwibGFzdF92YWx1ZSI6IjE4SyBHb2xkIFBsYXRlZCBIZWFydCBQZW5kYW50IE5lY2tsYWNlIn0>; rel='next'";

  // Extract just the URL.
  var match = RegExp(r'<([^>]*)>').firstMatch(testUrl);
  if (match != null) {
    var uri = Uri.parse(match.group(1)!);
    print(uri.queryParameters['page_info']); // Prints: eyJkaXJlY3Rpb24iOiJ...
  }
}

Note that the above would be simpler if testUrl were a proper URL without the angle brackets and rel='next' junk.