Elm decode json object with array - json

Question

Im totally new in ELM. Im trying to get data from get response.
Now im trying to make decoder for that. I have json like this:
{
data: [
{
"price" = 300.5
},
{
"price" = 1005
}
]
}
All i need is get lowest price and return it. (At least return each price).
Now i stacked on Decode.index.
priceDecoder : Decode.Decoder String
priceDecoder =
Decode.field "data" Decode.list
What should i do next?

Answer 1

There are several problems with the question itself. First, you're not posting the error you get. The error I get is this:
The 2nd argument to `field` is not what I expect:
25| Decode.field "data" Decode.list
^^^^^^^^^^^
This `list` value is a:
Decode.Decoder a -> Decode.Decoder (List a)
But `field` needs the 2nd argument to be:
Decode.Decoder a
Second, the JSON you've posted is not valid, data should be enclosed in quotes and properties and values should be separated by :, not =.
Thirdly, the type of priceDecoder seems wrong since the JSON contains no String data, or you're not specifying that you also want to convert the Float to a String. I will assume the type is just wrong.
So, the error you (or at least I) get says that list is a function Decoder a -> Decoder (List a), while it expects just a Decoder a value. This is because list expects a Decoder a to be passed to it, which it will use to decode each item in the list.
The decoder we'll use is Decode.field "price" Decode.float, which will decode the "price" field of the object as a Float.
I'll also change the type of priceDecoder from Decoder String to Decoder (List Float), since the price is a Float and we're decoding a List of them, not just getting the first or last value or something like that. I assume that's what you want since you say "at least return each price'.
The priceDecoder we get then is:
priceDecoder : Decode.Decoder (List Float)
priceDecoder =
Decode.field "data" (Decode.list (Decode.field "price" Decode.float))