selfie v1.0.0 Selfie

Provides a single way to access both a struct’s fields and its associated module’s functions.

Elixir structs know what module they belong to. Kernel.apply/3 lets you dynamically call module functions. Selfie takes advantage to let you play fast and loose with structs.

Warning: Dynamic function calls should often be avoided

Static analysis is a beautiful thing, and dynamic calls take some of that away. Be judicious about where you choose to use or not use Selfie. Where you wouldn’t use Kernel.apply/3, don’t use Selfie.self_apply/3.

Link to this section Summary

Functions

self_apply(struct, name, args_list \\ [])

Return the result of a struct field lookup or struct module function call

Link to this section Functions

self_apply(struct, name, args_list \\ [])

Return the result of a struct field lookup or struct module function call.

Arguments

struct - Any Elixir struct.

name - The name of a struct field or a function on the struct module.

args_list - An optional list of arguments to be passed in the case of a struct module function call.

Example

Define a struct module that includes some functions which take the struct as their first argument:

defmodule SelfieTest.Pair do
  defstruct x: nil, y: nil

  def sum(%Pair{x: x, y: y}), do: x + y

  def sum_modulo(pair, divisor), do: sum(pair) |> rem(divisor)
end

Selfie normalizes dynamic access to both fields and module functions. You can access a struct field:

iex> %Pair{x: 3, y: 4} |> self_apply(:x)
3

You can call a one-argument struct module function:

iex> %Pair{x: 3, y: 4} |> self_apply(:sum)
7

You can call a multi-argument struct module function:

iex> %Pair{x: 3, y: 4} |> self_apply(:sum_modulo, [6])
1