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This repo is a fork of https://github.com/vasspilka/bank example seasoned with Domo library in Command and Event modules.

That extended example is for "Eventsourcing and CQRS in Elixir" talk by Vasilis Spilka at ElixirConf EU 2021 https://youtu.be/GEFbhMZlxzE

Functions of Account context, process manager, and projector constructs commands and events with conformance to their types by calling to new/1 or new!.

That includes the validation of the account_number() value format via precondition defined in Bank module.

That brings the following errors to the User Interface automatically:

iex(1)> alias Bank.Core.Accounts
iex(1)> Accounts.deposit_money(nil, 10)        
{:error,
 [
   account_id: "Invalid value nil for field :account_id of %Bank.Core.Commands.DepositMoney{}. Expected the value matching the <<_::_*8>> type."
 ]}

iex(2)> Accounts.deposit_money("100102", 500)        
{:error, 
  [
    account_id: "Account number should be of xxx-xxx, x = 0..9 format."
  ]}

iex(3)> Accounts.deposit_money("100-102", -12)
{:error,
 [
   amount: "Invalid value -12 for field :amount of %Bank.Core.Commands.DepositMoney{}. Expected the value matching the non_neg_integer() type."
 ]}

iex(4)> Accounts.deposit_money("100-102", 120)
{:ok, %Commanded.Commands.ExecutionResult{}}

The casting of Event from Command with type mismatch produces runtime error.

The config :domo, :skip_defaults, true in config.exs is to disable verification of Commands and Events default values during compile time because fields are overwritten in Accounts context, Manager, and Projector anyway.

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