Joinable Dict

Join dictionaries like SQL does.

Make your container joinable

Check Dict.Joinable. OneToOne and ManyToOne modules are just two Joinable implementations that were suitable to my use case. The idea is to create yours. It would be a pleasure to merge a pull request of your joinable container.

Example

Join User and City dictionaries for matching ids in Dict:

import Dict exposing (Dict)
import Dict.OneToOne exposing (..)


type alias User = {...}
type alias City = {...}
type alias FavoritePub = {...}

type alias Database =
    { users : Dict Int User
    , cities : Dict Int City
    , favoritePubs : Dict Int FavoritePub
    }


type alias UserWithCity =
    { user : User
    , city : City
    , favoritePub : FavoritePub
    }

getUserWithCity : Database -> Dict Int UserWithCity
getUserWithCity db =
    select UserWithCity
        |> from db.users
        |> innerJoin db.cities
        |> innerJoin db.favoritePubs

SQL Equivalent for getUserWithCity function:

SELECT *
FROM users
INNER JOIN cities
    ON users.id = cities.id
INNER JOIN favoritePubs
    ON users.id = favoritePubs.id

Note that we always take Dict key for join match in this package so we don't use ON like SQL does.