Hey folks,

I’m pleased to announce StructyRecord, my very first Elixir library!

• GitHub - https://github.com/sunaku/structy_record
• Hex.pm - https://hex.pm/packages/structy_record

I created this library to improve the usability of Records (which are clunky to use in comparison to the first-class language support for Structs) because my performance-sensitive Elixir applications make heavy use of ETS tables that rely on Records for data representation.

I hope that it’s also useful to you, enjoy!

Cheers.

Readme

StructyRecord provides a Struct-like interface for your Records.

• Use your record’s macros in the same module where it is defined!
• Access and update fields in your record through named macro calls.
• Create and update records at runtime (not limited to compile time).
• Calculate 1-based indexes to access record fields in :ets tables.

To get started, see the documentation for StructyRecord.defrecord/3:

iex> h StructyRecord.defrecord

Features

The defined module provides the following guards, macros, and functions.

Guards:

• is_record/1 to check if argument loosely matches this record’s shape

Macros:

• record?/1 to check if argument strictly matches this record’s shape
• record/0 to create a new record with default values for all fields
• record/1 to create a new record with the given fields and values
• record/1 to get the zero-based index of the given field in a record
• record/1 to convert the given record into a Keyword list
• record/2 to get the value of a given field in a given record
• record/2 to update an existing record with the given fields and values
• ${field}/1 to get the value of a specific field in a given record
• ${field}/2 to set the value of a specific field in a given record
• keypos/1 to get the 1-based index of the given field in a record

Functions:

• record!/1 to create a new record at runtime with the given fields and values
• record!/2 to update an existing record with the given fields and values

Examples

Activate this macro in your environment:

require StructyRecord

Define a structy record for a rectangle:

StructyRecord.defrecord Rectangle, [:width, :height] do
  def area(r=record()) do
    width(r) * height(r)
  end

  def perimeter(record(width: w, height: h)) do
    2 * (w + h)
  end

  def square?(record(width: same, height: same)), do: true
  def square?(_), do: false
end

Activate its macros in your environment:

use Rectangle

Create instances of your structy record:

rect = Rectangle.record()                      #-> {Rectangle, nil, nil}
no_h = Rectangle.record(width: 1)              #-> {Rectangle, 1, nil}
no_w = Rectangle.record(height: 2)             #-> {Rectangle, nil, 2}
wide = Rectangle.record(width: 10, height: 5)  #-> {Rectangle, 10, 5}
tall = Rectangle.record(width:  4, height: 25) #-> {Rectangle, 4, 25}
even = Rectangle.record(width: 10, height: 10) #-> {Rectangle, 10, 10}

Get values of fields in those instances:

tall |> Rectangle.height()            #-> 25
tall |> Rectangle.record(:height)     #-> 25
Rectangle.record(height: h) = tall; h #-> 25

Set values of fields in those instances:

even |> Rectangle.width(1)         #-> {Rectangle, 1, 10}
even |> Rectangle.record(width: 1) #-> {Rectangle, 1, 10}

even |> Rectangle.width(1) |> Rectangle.height(2) #-> {Rectangle, 1, 2}
even |> Rectangle.record(width: 1, height: 2)     #-> {Rectangle, 1, 2}

Use your custom code on those instances:

rect |> Rectangle.area() #-> (ArithmeticError) bad argument in arithmetic expression: nil * nil
no_h |> Rectangle.area() #-> (ArithmeticError) bad argument in arithmetic expression: 1 * nil
no_w |> Rectangle.area() #-> (ArithmeticError) bad argument in arithmetic expression: nil * 2
wide |> Rectangle.area() #-> 50
tall |> Rectangle.area() #-> 100
even |> Rectangle.area() #-> 100

rect |> Rectangle.perimeter() #-> (ArithmeticError) bad argument in arithmetic expression: nil + nil
no_h |> Rectangle.perimeter() #-> (ArithmeticError) bad argument in arithmetic expression: 1 + nil
no_w |> Rectangle.perimeter() #-> (ArithmeticError) bad argument in arithmetic expression: nil + 2
wide |> Rectangle.perimeter() #-> 30
tall |> Rectangle.perimeter() #-> 58
even |> Rectangle.perimeter() #-> 40

rect |> Rectangle.square?() #-> true
no_h |> Rectangle.square?() #-> false
no_w |> Rectangle.square?() #-> false
wide |> Rectangle.square?() #-> false
tall |> Rectangle.square?() #-> false
even |> Rectangle.square?() #-> true