View Source Commanded.Aggregate.Multi (Commanded v1.4.1)
Use Commanded.Aggregate.Multi
to generate multiple events from a single
command.
This can be useful when you want to emit multiple events that depend upon the aggregate state being updated.
example
Example
In the example below, money is withdrawn from the bank account and the updated balance is used to check whether the account is overdrawn.
defmodule BankAccount do
alias Commanded.Aggregate.Multi
defstruct [:account_number, :state, balance: 0]
def withdraw(
%BankAccount{state: :active} = account,
%WithdrawMoney{amount: amount})
when is_number(amount) and amount > 0
do
account
|> Multi.new()
|> Multi.execute(&withdraw_money(&1, amount))
|> Multi.execute(&check_balance/1)
end
defp withdraw_money(%BankAccount{account_number: account_number, balance: balance}, amount) do
%MoneyWithdrawn{
account_number: account_number,
amount: amount,
balance: balance - amount
}
end
defp check_balance(%BankAccount{account_number: account_number, balance: balance})
when balance < 0
do
%AccountOverdrawn{account_number: account_number, balance: balance}
end
defp check_balance(%BankAccount{}), do: []
end
Link to this section Summary
Functions
Adds a command execute function to the multi.
Create a new Commanded.Aggregate.Multi
struct.
Reduce an enumerable by executing the function for each item.
Run the execute functions contained within the multi, returning the updated aggregate state and all created events.
Link to this section Types
Link to this section Functions
Adds a command execute function to the multi.
Create a new Commanded.Aggregate.Multi
struct.
Reduce an enumerable by executing the function for each item.
The aggregate apply/2
function will be called after each event returned by
the execute function. This allows you to calculate values from the aggregate
state based upon events produced by previous items in the enumerable, such as
running totals.
example
Example
alias Commanded.Aggregate.Multi
aggregate
|> Multi.new()
|> Multi.reduce([1, 2, 3], fn aggregate, item ->
%AnEvent{item: item, total: aggregate.total + item}
end)
Run the execute functions contained within the multi, returning the updated aggregate state and all created events.