RieMap

Operators for working with JSON objects of unknown structure.

Content

• RieMap
  • Content
  • Installation
  • Motivation
  • Example
  • Different forms

Installation

You can get yourself a brand new copy of RieMap for FREE! (crazy, I know...) Just use the following command:

npm i riemap

Motivation

Long story short, I was working on a CMS system, which allowed users to edit db models, thus I didn't know data-types of fetched items ahead of time. As you may know, Reason doesn't allow for dynamic records. It made my use arrays of tuples, a.k.a. (key => value) pairs. Dealing with it was kinda tedious, so I decided to write a simple lib around it.

Example

Let's pretend a user wants to access a collection of kittens. Needless to say you had to prepare the structure in advance on the backend.

let fetchedKittens = Fetch.kittensSync() |> Json.parseDynamic
/*
  => [|
    ("Fluffykins#001", [|
      ("Age", "3"), <-- They all have to be of the same type;
      ("Breed", "Ragdoll")
    |]),
    ("Fluffykins#002", [|
      ("Age", "1"),
      ("Breed", "Ragdoll")
    |]),
    ("Toby#001", [|
      ("Age", "3"),
      ("Breed", "Birman")
    |])
  |]
*/

So now you've got this ugly mess of a structure, just because the user may want to change the fields anytime. Good for you!(unsarcastic cough) Alright, time to deal with it! Let's start with simply getting the Fluffykins#001.

let fluffykins001 = fetchedKittens @: "Fluffykins#001"
/*
  => Some([|
    ("Age", "3"),
    ("Breed", "Ragdoll")
  |])
*/

Oh... forgot to tell you that @: (or if you prefer the function form get()) returns an option('a), as what would happen if you tried accessing let's say, Bobby#001? As you can see, such kitten doesn't exist, so instead of throwing an error, you would just get None and let the user know. But if you're feeling adventures, you may just use @:! (or getUnsafe()). Let's stick with it just for simplicity's sake.

let fluffykins001 = fetchedKittens @:! "Fluffykins#001"

// Now let's say that we want to get it's breed.
let breed = fluffykins001 @:! "Breed" 
// => "Ragdoll"

Cool things, right? Ok, let's say it's just been Fluffykins's birthday (Happy birthday Fluffy :tada:), so now it's 4, not 3. Time to update that!

let newKittens = fetchedKittens 
  @# (
    "Fluffykins#001", 
    fluffykins001 @# ("Age", "4")
  )

/*
  => [|
    ("Fluffykins#001", [|
      ("Age", "4"), <-- Now it's 4 years old!
      ("Breed", "Ragdoll")
    |]),
    ("Fluffykins#002", [|
      ("Age", "1"),
      ("Breed", "Ragdoll")
    |]),
    ("Toby#001", [|
      ("Age", "3"),
      ("Breed", "Birman")
    |])
  |]
*/

Let me quickly walk you through. @# takes a key (Fluffykins#001) and a new value for the entry. The value is our fluffykins001 with the changed age. Ok, that was pretty awesome, but we hard-coded the age of 4. Let's rewrite the code such that it uses a dynamic age.

let newKittens = fetchedKittens
  @#> (
    "Fluffykins#001", 
    fluffykins => fluffykins 
      @# (
        "Age",
        (int_of_string(fluffykins @:! "Age") + 1)
          |> string_of_int
      )
  )

Here's how the @#> operator works. Instead of taking a new value, it takes a function ('a) => 'a.

Different forms

| Function | Operator | | ------------------------------------------ | -------- | | get(t('a), string) => option('a) | @: | | getOr(t('a), string, 'a) => 'a | @| | | getUnsafe(t('a), string) => 'a | @:! | | remove(t('a), string) => t('a) | @- | | concat(t('a), t('a)) => t('a) | @++ | | push(t('a), 'a) => t('a) | @+ | | replace(t('a), string, 'a) => t('a) | @# | | freplace(t('a), string, 'a => 'a) => t('a) | @#> | | map(t('a), string, 'a => 'b) => array('b) | @>>= | | getRe(t('a), Js.Re.t) => array('a) | $: | | aggregate(t('a), Js.Re.t) => t('a) | $:: |