JavaScript can do an http request with closure, but how does that work in Elm?

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1

In JavaScript it’s pretty common to use closures, very handy for example when making http requests, and remembering what you asked for. I.e.

var id = 3;
http_request (function (result) {
  // I know I made the request for id 3, 
  // even though the result variable may not mention this
});

How do you do this in Elm? It seems that in Elm the result needs to tell my program what it was for.

Any suggestions?

2

Need more coffee in the morning :slight_smile: But as usual. phrasing the question is answering it, so may have helped me.

This is how to do it obviously:

Http.send (Foo id) request

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3

What’s foo msg signature and request implementation? I need more details.

4 
request = 
    Http.get "/foo" decodeResponse

Msg =
    Foo Int (Result Http.Error ValidResponse)

In case it isn’t clear, I answered my own question.

5

request : Http.Request ValidResponse
request = Http.get “/foo” decodeResponse

type Msg = Foo Int (Result Http.Error ValidResponse)

Now I noticed that you already solved your problem. This is a nice way, but if I would need this information later, I would store in the model instead of passing in the first parameter. But you did right for your case

6

The problem is that this does not work: http requests are asynchronous, so you cannot control when a response is received, so you cannot match a state in your model against a randomly incoming response. It might be a delayed and stale response.

7

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