Edit

Query parameters

In addition to working with routes, the library also defines parser combinators for working with ? queries:

  • <?> combinator for query parameters,
  • stringParam combinator to extract a string,
  • intParam combinator to attempt to parse an int.

Some examples:

open Elmish.UrlParser

type PersonQuery =
    { name: string
      age: int }

type Route =
    | Blog of int
    | Search of string option
    | Query of PersonQuery option

    with static member FromParams name age =
        match name,age with
        | Some name, Some age -> Query (Some { name = name; age = age})
        | _ -> Query None


let route : Parser<Route->Route,_>=
    oneOf
        [ map Search (s "blog" <?> stringParam "search")
          map Blog (s "blog" </> i32)
          map (Route.FromParams) (top <?> stringParam "name" <?> intParam "age") ]

Note that unlike route combinators, which fail to match the entire route if some combinator can not be parsed, query param parsers return Option. It's up to you if you decide to accept a query parameter as None.

The parser above will resolve:

    blog/              ==>  Some (Search None)
    blog?search=cats   ==>  Some (Search (Some "cats"))
    blog/42            ==>  Some (Blog 42)
    ?name=tom&age=42   ==>  Some (Query {name="tom"; age=42})
    ?name=tom          ==>  Some (Query None)
←Parsing routes