Dart: convert map into query string

Question

I have a situation where I need to turn a Map into a query String (after the first ?). For instance if I have the following map:

Map json = {
    "email":  eml,
    "password": passwd
};

And a base URL:

String baseURL = "http://localhost:8080/myapp";

Then I need something that converts the json Map into the query string of the base URL:

String fullURL = parameterizeURL(baseURL, json);

// Prints: http://localhost:8080/myapp?email=blah&password=meh
// (if "blah" was entered as the email, and "meh" was entered as the password)
print(fullURL);

I found this query String-to-map library on Git, but I need the inverse of this! It would be great to get URL encoding in there as well.

I'm happy to make something homegrown but being so new to Dart I was wondering if there's anything on pub/Github/the etherspehere that does this already.

Answer 1

Have you looked at the Uri class in dart:core. You can construct a Uri class from Url components :

new Uri({String scheme, String userInfo: "", String host: "", port: 0, String path, 
  Iterable<String> pathSegments, String query, 
  Map<String, String> queryParameters, fragment: ""}) #

Notice you pass the query string as a map, if you are using a HTTP client that doesn't take this class you can .toString it to get the Url.

I use this in my code rather than string Url's

As an example using your data above :

void main() {

      String eml = "[email protected]";
      String passwd = "password";

      Map json = {
                  "email":  eml,
                  "password": passwd
      };  


      Uri outgoingUri = new Uri(scheme: 'http',
          host: 'localhost',
          port: 8080,
          path: 'myapp',
          queryParameters:json);

      print(outgoingUri);

    }

This prints :

http://localhost:8080/myapp?email=me%40here.com&password=password

Note that once constructed a Uri is immutable, i.e. you can't change the query parameters again. There is also this package in pub which may give more facilities although I've not used it yet.