Hi, all. I have read several elixir books and the only Ecto book, and still confused on Typespecs. I googled a few articles on typespecs including official Typespect document of Elixir site and questions in elixir forum here, but not clear at all. For example, defmodule Friends.Person do use Ec…

The first parameter of the changeset function is the person struct, and the second is a map . Can the type of the person struct be denoted as {map, map}? No. I guess the person struct is something like %MyApp.Person{ name: "John Doe", gender: "male" } In Elixir, this is just %{ __struct_…

Let’s do this from the outside in: changeset/2 has an arity of 2 (ignoring the default for now, typespecs don’t know about default values) and as any function one return value. The return value is simple: Ecto.Changeset.t, which essentially aliases an Ecto.Changeset struct. Parameter 1 is {map, m…

Hi LostKobrakai . I have thankfully read several articles of you written before. The first parameter of the changeset function is the person struct, and the second is a map. Can the type of the person struct be denoted as {map, map}? What is the meaning of the two lowdash ‘__’ before and after some…

Would anyone write the typespecs of the changeset function by hand without Dialyzer? My guess is; @spec changeset(Person.t(), %{optional(key) => value}) :: Changeset.t() Seeing the Typespecs page, the built-in type of struct() is defined as %{:__struct__ => atom(), optional(atom()) => any()}. I…

Now I understand some of the crypto codes. Would you show me the typespecs of the changeset function if you write it rather than those of Dialyzer? And what is meaning of {map, map} in the typespecs above?

Ecto.Changeset.cast/4 has its first argument typed as Ecto.Schema.t() | t() | {data(), types()}. So the {map, map} is coming from that last argument type, which is a tuple of two maps (both data() and types() are just aliases to map() in Ecto code).

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jejuro December 15, 2020, 9:24am 9

Thank you, Nicd.
Much more clear than before.