records.md

Records

Records are data structures that have a fixed set of keys.

You can define a record type with the record keyword:

record User {
  email : String,
  name : String,
  id : Number
}

{% hint style="info" %} Records cannot have types which have type variables. {% endhint %}

{% hint style="warning" %} Record definitions are globally unique, so defining a record with the same structure but a different name will raise an error. {% endhint %}

Nested records

Records can be nested in each other, using nested type definitions.

record Position {
  x : Number,
  y : Number
}

record Entity {
  position : Position,
  id : String
}

Creating a nested record is straightforward:

entity =
  {
    position = {
      x = 0,
      y = 0
    },
    id = "0"
  }

Working with records

Records can be created like this:

{
  email = "john.doe@gmail.com",
  name = "John Doe",
  id = 0
}

You can create a new record by copying from an existing one and changing only some of the fields, like this:

user =
  {
    email = "john.doe@gmail.com",
    name = "John Doe",
    id = 0
  }

updatedUser =
  { user | name = "Stuart" }

{
  email = "john.doe@gmail.com",
  name = "Stuart",
  id = 0
}

{% hint style="warning" %} Trying to add fields to a record which doesn't have it in it's definition will raise an error. {% endhint %}

{% hint style="info" %} [PLANNED] You can update a nested record with a dot notation. {% endhint %}

user =
  {
    name = "Stuart",
    address = {
      location = "Freedonia"
    }
  }

{ user |
  name = "Bob",  
  address.location = "Super Silly Fun Land"
}