Lenses.elm

module Model.Lenses exposing (..)

-- other imports omitted
import Monocle.Optional as MO
import RemoteData


entryInList : String -> MO.Optional (List Entry) Entry
entryInList id =
    { getOption = List.Extra.find (\entry -> entry.id == id)
    , set =
        (\newEntry entries ->
            List.map
                (\entry ->
                    if entry.id == id then
                        newEntry
                    else
                        entry
                )
                entries
        )
    }


entriesInModel : MO.Optional Model (List Entry)
entriesInModel =
    { getOption = .entries >> RemoteData.toMaybe
    , set =
        (\newEntries model ->
            { model | entries = RemoteData.Success newEntries }
        )
    }


entryInModel : String -> MO.Optional Model Entry
entryInModel id =
    MO.compose entriesInModel (entryInList id)

Model.elm

-- Stuff up here

type alias Model =
    { route : Router.Route
    , showSidebar : Bool
    , journals : WebData (List Journal)
    , entries : WebData (List Entry)
    , editor : Savable String
    , notification : Notification.Model
    }