genre.md

Genre

Moving to our next WebPart "browse", let's first adjust it in View module:

let browse genre (albums : Db.Album list) = [
    h2 (sprintf "Genre: %s" genre)
    ul [
        for a in albums ->
            li (aHref (sprintf Path.Store.details a.AlbumId) (text a.Title))
    ]
]

so that it takes two arguments: name of the genre (string) and a list of albums for that genre. For each album we'll display a list item with a direct link to album's details.

Note: Here we used the Path.Store.details of type IntPath in conjunction with sprintf function to format the direct link. Again this gives us safety in regards to static typing.

Now, we can modify the browse WebPart itself:

let browse =
    request (fun r ->
        match r.queryParam Path.Store.browseKey with
        | Choice1Of2 genre -> 
            Db.getContext()
            |> Db.getAlbumsForGenre genre
            |> View.browse genre
            |> html
        | Choice2Of2 msg -> BAD_REQUEST msg)

Again, usage of pipe operator makes it clear what happens in case the genre is resolved from the query parameter.

Note: in the example above we adopted "partial application", both for Db.getAlbumsForGenre and View.browse. This could be achieved because the return type between the pipes is the last argument for these functions.

If you navigate to "/store/browse?genre=Latin", you may notice there are some characters displayed incorrectly. Let's fix this by setting the "Content-Type" header with correct charset for each HTTP response:

let html container =
    OK (View.index container)
    >>= Writers.setMimeType "text/html; charset=utf-8"