How to get the struct type in Elixir

So you don’t know what’s the type of struct you’re passing somewhere? Maybe it can be one of few types and you have to distinguish them? Or any other reason… But it’s about checking the struct type. Just use one of the coolest Elixir features - pattern matching!

Table of contents

    Check this out:

    iex(1)> some_struct = %MyApp.User{}
    iex(2)> %type{} = some_struct
    iex(3)> type
    MyApp.User

    That’s just a hook point for a bunch of cool facilities, like function call by module type:

    defmodule Chess.Bishop do
      def move(piece), do: move_diagonally(piece)
    end
    
    defmodule Chess.Rook do
      def move(piece), do: move_straight(piece)
    end
    
    defmodule Chess.Pawn do
      def move(piece), do: move_forward(piece)
    end

    And then in console:

    iex(1)> piece = get_chess_piece()
    iex(2)> %module{} = piece
    iex(3)> module.move(piece)

    Have fun! If you'd like to learn more about structs in Elixir, check this blog post: Elixir Trickery: Cheating on Structs, And Why It Pays Off.

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    Oskar Legner
    Oskar Legner Elixir & React Developer

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