https://github.com/chadtech/elm-relational-database

Manage remote data with ids in your front end
https://github.com/chadtech/elm-relational-database

elm relational-databases

Last synced: 2 months ago
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Manage remote data with ids in your front end

• Host: GitHub
• URL: https://github.com/chadtech/elm-relational-database
• Owner: Chadtech
• License: other
• Created: 2019-04-19T11:46:21.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2019-04-22T15:01:21.000Z (over 5 years ago)
• Last Synced: 2024-04-15T01:18:10.740Z (9 months ago)
• Topics: elm, relational-databases
• Language: Elm
• Homepage: https://package.elm-lang.org/packages/Chadtech/elm-relational-database/latest
• Size: 28.3 KB
• Stars: 9
• Watchers: 3
• Forks: 1
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Elm Relational Database

Some software projects involve the front end handling a large amount of unknown, dynamic and inter-related data, often retrieved from a remote source. Heres what I mean, taking a `User` as an example..

- `Large` meaning, the front end might get a lot of `User`s.

- `Unknown` meaning, it has no idea how many or what `User`s it will get

- `Inter-related` meaning, `User`s might be related to other data, for example your software might let `User` be friends with each other. 

- `Dynamic` meaning, the `User`s and their relationship might change over time. A new `User` might show up, or, two existing `User`s might become friends with each other during or between run times.

Projects like this need a centralized single source of truth for all this data, so so that your data can be represented the same across the entire software. Indeed, thats exactly what a relational database is. 

```elm

import Db exposing (Db)

type alias Model =

    { users : Db User }

```

[If you still are wondering what the deal is, Richard Feldman gave a really good talk on relational database stuff in Elm.](https://www.youtube.com/watch?v=28OdemxhfbU)

## Message Board Example

```elm

import Db exposing (Db)

import Id exposing (Id)

type alias Model =

    { threads : Db Thread

    , posts : Db Post

    }

type alias Thread =

    { title : String

    , posts : List (Id Post)

    }

type alias Post =

    { author : String

    , content : String

    }

-- ..

threadView : Db Post -> (Id Thread, Thread) -> Html Msg

threadView postsDb (threadId, thread) =

    let

        posts : List (Html Msg)

        posts =

            thread.posts

                |> Db.getMany postsDb

                |> Db.filterMissing 

                |> List.map postView

    in

    Html.div [ css [ threadStyle ] ]

        (Html.p [] [ Html.text thread.title ] :: posts)

postView : (Id Post, Post) -> Html Msg

postView (id, post) =

    Html.div

        [ Attrs.css [ postStyle ] ]

        [ Html.p

            []

            [ Html.text post.author ]

        , Html.p

            [ Event.onClick (ReplyToPostClicked id) ]

            [ Html.text post.content ]

        ]

```