Using F# template for ASP.NET MVC. Have routes defined a la
app.UseRouting()
.UseEndpoints(fun endpoints ->
endpoints.MapGet("/", fun context ->
context.Response.WriteAsync(PageController.loadHomePage())) |> ignore
endpoints.MapGet("/contact", fun context ->
context.Response.WriteAsync(PageController.loadContactPage())) |> ignore
endpoints.MapGet("/about", fun context ->
context.Response.WriteAsync(PageController.loadAboutPage())) |> ignore
And then controller functions which all load the same page and simply sub in a title variable. The addVariable function simple replaces all instances of "[title]" with the string provided when loadTemplate is called.
module PageController
let loadHomePage() =
Theme.addVariable "title" "Home Page"
Theme.loadTemplate "index"
let loadContactPage() =
Theme.loadTemplate "index"
let loadAboutPage() =
Theme.addVariable "title" "About Us"
Theme.loadTemplate "index"
However when I navigate to /contact, which does not a have a title variable defined, it has a title of "Home Page" which means loadHomePage() is being run and setting the title variable.
Am new to ASP.NET and F# so assuming it's super simple.
Edit:
(* Add variable function adds a value to a dictionary *)
let mutable themeVars = new Dictionary<string, string>()
let addVariable name value =
themeVars.[name] <- value
(* Load template, opens a file and runs "parseVariables" on the content *)
let ParseVariables (string:string) =
Regex.Replace(string, "\[(.*?)\]",
new MatchEvaluator(
fun matchedVar ->
let varName = matchedVar.Groups.[1].ToString()
|> StringTrim
if themeVars.ContainsKey varName then
themeVars.[varName]
else
"[Undefined Variable: " + varName + "]"
))
let loadTemplate templateName =
if templateExists templateName then
templateName
|> getTemplateFilePath
|> File.ReadAllText
|> ParseVariables
else
"Missing Template: " + templateName + ""
I think the problem here is that you have a single mutable themeVars dictionary that is shared by all three pages. When your app starts, the home page is loaded, which adds a variable named "Title" to the dictionary. Then, when you visit the Contact page, that variable is still present in the dictionary, with whatever value it had last. (Could be either "Home Page" or "About Us".)
To avoid this, create a separate immutable variable lookup for each page instead. Something like this:
let loadHomePage() =
let themeVars = Map [ "Title", "Home Page" ]
Theme.loadTemplate themeVars "index"
let loadContactPage() =
let themeVars = Map.empty
Theme.loadTemplate themeVars "index"
let loadAboutPage() =
let themeVars = Map [ "Title", "About Us" ]
Theme.loadTemplate themeVars "index"
Note that I've used a Map here instead of a Dictionary, since they're easier to deal with in F#, but the idea is the same either way.
Related
I have the following graphQL result:
[Just { details = Just "Engine failure at 33 seconds and loss of
vehicle", launch_year = Just "2006", links = Just { article_link =
Just
"https://www.space.com/2196-spacex-inaugural-falcon-1-rocket-lost-launch.html"
}, mission_name = Just "FalconSat" }]
Based on the following types:
type alias Launch =
{ mission_name : Maybe String
, details : Maybe String
, launch_year : Maybe String
, links : Maybe LaunchLinks
}
type alias Launches =
Maybe (List (Maybe Launch))
type alias LaunchLinks =
{ article_link : Maybe String
}
I want to List.map through and display the results in unordered list. I started with this:
renderLaunch : Launches -> Html Msg
renderLaunch launches =
div [] <|
case launches of
Nothing ->
[ text "Nothing here" ]
Just launch ->
launch
|> List.map (\x -> x)
|> ul []
But I keep getting this error:
This function cannot handle the argument sent through the (|>) pipe:
141| launch 142| |> List.map (\x
-> x) 143| |> ul []
^^^^^ The argument is:
List (Maybe Launch)
But (|>) is piping it a function that expects:
List (Html msg)
The problem is that the Just launch case needs to result in a List (Html msg) but the code results in a different type being returned.
When you are using List.map (\x -> x), it is essentially a no-op. You are iterating over a List (Maybe Launch) and returning the same thing. I'd recommend creating another function that takes a Maybe Launch value and use that as your mapping function. For example:
displayLaunch : Maybe Launch -> Html Msg
displayLaunch launch =
case launch of
Nothing -> text "No launch"
Just l -> text (Debug.toString l)
Now you can plug that into your mapping function:
Just launch ->
launch
|> List.map displayLaunch
|> ul []
But, whoops! Now you get a new error indicating:
The 2nd branch is:
Html Msg
But all the previous branches result in:
List (Html msg)
The problem here is that we are now returning a ul from the Just launch branch and we need to return a list of html. You can use List.singleton to create a list with just one item:
Just launch ->
launch
|> List.map displayLaunch
|> ul []
|> List.singleton
For the sake of learning, I'm trying to load content only when I click on a button. So far I've managed to :
Reload the content when I click the button.
And Filter the Signal when I click (if the String I send is not "GETPERF")
But my problem is that the Ajax call is still triggered once the page loads.
Here's the code:
-- SIGNALS & MAILBOX
inbox : Signal.Mailbox String
inbox =
Signal.mailbox "SOME TEXT"
result : Signal.Mailbox String
result =
Signal.mailbox ""
-- VIEW
view : String -> Html
view msg =
div [] [
h1 [] [text "Mailbox3"],
p [] [text msg],
button
[onClick inbox.address "GETPERF"]
[text "click perf"],
]
main : Signal Html
main =
Signal.map view result.signal
-- TASK & EFFECTS
port fetchReadme : Signal (Task Http.Error ())
port fetchReadme =
inbox.signal
|> Signal.filter (\sig -> sig == "GETPERF" ) "boo"
|> Signal.map (\_ -> Http.getString "http://localhost:3000/dates" `andThen` report)
report : String -> Task x ()
report html =
Signal.send result.address html
Is there any way to prevent the first Ajax call on page load ? (Or some more idiomatic way of doing all this ?)
The reason you're getting an initial ajax request is that Signal.filter is still keeping that initial value of "boo" (See the Signal.filter documentation here). That value is ignored in the next Signal.map statement by your use of the underscore parameter, but the Http Task is still getting returned and that's why you see an initial ajax request on page load.
Instead of using Signal.filter, you could write a conditional that only sends the ajax request in the correct circumstances, when sig is "GETPERF". And if sig is not "GETPERF" (as in page load), you can, in essence, do nothing by returning Task.succeed (). Here is a refactored fetchReadme function with these changes:
port fetchReadme : Signal (Task Http.Error ())
port fetchReadme =
let
fetchAndReport sig =
if sig == "GETPERF" then
Http.getString "http://localhost:3000/dates"
`andThen` report
else
Task.succeed ()
in
Signal.map fetchAndReport inbox.signal
In my Elm program, I'd like to initialize my model based on the query string.
For example, if the query string is ?w=3&h=5 I'd like to have:
initialModel =
{ width = 3
, height = 5
}
Is that possible to achieve this in Elm, or the only way to do this is to get the query parameters in Javascript and pass them via a port?
Elm 0.19
For elm 0.19 the below concept is the same. Both of these packages still exist but have been moved and relabeled as the official elm/url and elm/browser libraries.
Elm 0.18
This example uses evancz/url-parser and elm-lang/navigation. There are a few kinks that aren't straightforward in the documentation, but I've explained them briefly below. The example should speak for itself.
module Main exposing (..)
import Html as H exposing (..)
import Navigation exposing (Location)
import UrlParser as UP exposing ((</>), (<?>), top, parsePath, oneOf, s, stringParam, Parser)
import Maybe.Extra as MaybeExtra exposing (unwrap)
type Route
= UrlRoute (Maybe String) (Maybe String)
| NotFoundRoute
type Msg
= UrlParser Navigation.Location
type alias Model =
{ location : Route
, w : String
, h : String
}
type alias SearchParams =
{ w : Maybe String, h : Maybe String }
main =
Navigation.program UrlParser
{ init = init
, view = view
, update = update
, subscriptions = (\_ -> Sub.none)
}
init : Location -> ( Model, Cmd Msg )
init location =
let
currentPath =
parseLocation location
in
( initialModel currentPath
, Cmd.none
)
parseLocation : Location -> Route
parseLocation location =
case (parsePath matchers location) of
Just route ->
route
Nothing ->
NotFoundRoute
matchers : Parser (Route -> a) a
matchers =
UP.map UrlRoute (UP.s "index" <?> UP.stringParam "w" <?> UP.stringParam "h")
initialModel : Route -> Model
initialModel route =
{ location = route
, w = MaybeExtra.unwrap "" (\x -> Maybe.withDefault "" x.w) (parseParams route)
, h = MaybeExtra.unwrap "" (\x -> Maybe.withDefault "" x.h) (parseParams route)
}
parseParams : Route -> Maybe SearchParams
parseParams route =
case route of
UrlRoute w h ->
Just { w = w, h = h }
NotFoundRoute ->
Nothing
update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
UrlParser location ->
( model
, Cmd.none
)
view : Model -> Html msg
view model =
div []
[ h1 [] [ text "URL Info" ]
, div [] [ text ("W is: " ++ model.w) ]
, div [] [ text ("H is: " ++ model.h) ]
]
The "trick" is to create another type alias to place your query params inside of. In the above example I've created the type SearchParams. After creating this type we just use an initialModel that takes in the currentPath.
From there, our model can extract the query params with Maybe.withDefault (it needs to be a Maybe type because the params may not be there). Once we have our data in the model we just print it out in the view.
Hope this helps!
There is no built-in core library way to access the URL. You can use ports and the community library jessitron/elm-param-parsing.
If you also want to set the URL, you can again use ports, or you can use the History API, for which there are bindings in TheSeamau5/elm-history.
Unfortunately jessitron/elm-param-parsing doesn't work with Elm 0.18.
Use elm-lang/navigation package:
http://package.elm-lang.org/packages/elm-lang/navigation/latest/Navigation
https://github.com/elm-lang/navigation/tree/2.1.0
especially this function:
program
: (Location -> msg)
-> { init : Location -> (model, Cmd msg), update : msg -> model -> (model, Cmd msg), view : model -> Html msg, subscriptions : model -> Sub msg }
-> Program Never model msg
In the second parameter you can see "init : Location -> (model, Cmd msg)". This should handle reading of initial URL. To complement that, first parameter is a function which gets called every time URL changes.
(I am aware it's an old question, but this link popped out when I was looking for the solution to the same problem and accepted answer didn't help)
I've been trying to authenticate the bitstamp api however, I keep on getting the following error:
"{\"error\": \"Missing key, signature and nonce parameters\"}"
The code I have written to do this is below:
let nounce = System.DateTime.Today.Ticks
let hexdigest (bytes : byte[]) =
let sb = System.Text.StringBuilder()
bytes |> Array.iter (fun b -> b.ToString("X2") |> sb.Append |> ignore)
string sb
let signature =
use hmac = new HMACSHA256(System.Text.Encoding.ASCII.GetBytes(stampsecret))
hmac.ComputeHash(mes)
|> hexdigest
I am calling the website with the following:
let ordersBTCbuy()=
Http.Request("https://www.bitstamp.net/api/buy", meth="Post", query=["key", stampkey; "signature", signature.ToLower(); "nonce", string(nounce); "amount", "1"; "price", string(convertB)])
A reference to the API can be found here: https://www.bitstamp.net/api/
Update I've changed the web address to:
let ordersBTCbuy()=
Http.Request("https://www.bitstamp.net/api/buy/", meth="Post", query=["key", stampkey; "signature", signature.ToLower(); "nonce", string(nounce); "amount", "1"; "price", string(convertB)])
My new issue is now the signature my representation is 64 characters long and upper case however I still seem to have an error.
When creating a POST request. Your key-value pairs need to go in the body.
To do that using FSharp data do the following:
let postBody = FormValues([ "key", stampkey; "signature", signature.ToLower(); "nonce", string(nounce); "amount", "1"; "price", string(convertB)])
let ordersBTCbuy()=
Http.Request("https://www.bitstamp.net/api/buy", httpMethod="Post", body=postBody)
what am I doing wrong here?
I have a model for an app I am writing called page. Those attributes are:
title
pagetype
page_url
title and pagetype can be set as normally, but I used a custom getter/setter for the page_url. Here is the logic/model:
class Page < ActiveRecord::Base
def page_url=()
temp = self[:title]
pageUrl = temp.gsub(" ", "_").downcase
if self[:pagetype] == "home"
pageUrl = "/"
end
self[:page_url] = pageUrl
end
def page_url
self[:page_url]
end
end
It's fairly simple -> page_url is based on the title with all spaces replaced with unless page_type == "home", which then gets set to "/". For the record I don't want to make page_url virtual because I need it to be searchable and saved in the db.
So unfortunately whether in rails console or my app this is failing. Here is how I am calling the setter method in the console;
page1 = Page.new
page1.pagetype = "home"
page1.title = "this is a test"
page2 = Page.new
pager2.pagetype = "content"
page2.title = "this is another test"
#expected results should be
page1.page_url()
=> "/"
page2.page_url()
However I keep getting this:
page1.page_url()
=> nil
What the heck am I doing wrong here?
These custom setter and getters don't persist to the database. If you have a column page_url in your database, you can set the value with a callback. E.g. before_save:
class Page < ActiveRecord::Base
before_save :set_page_url
def set_page_url
if self[:pagetype] == "home"
self.page_url = "/"
else
self.page_url = self[:title].gsub(" ", "_").downcase
end
end
end