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Contents
defmodule BankAccount do
@moduledoc """
A bank account that supports access from multiple processes.
"""
use GenServer
## Callbacks
def init(_args) do
{:ok, 0}
end
def handle_call(:balance, _from, balance) do
{:reply, balance, balance}
end
def handle_call({:update, amount}, _from, balance) do
{:reply, :ok, balance + amount}
end
def handle_call(:close, _from, balance) do
# We stop normally and return :stopped to the caller.
{:stop, :normal, :stopped, balance}
end
## Interface for tests
@typedoc """
An account handle.
"""
@opaque account :: pid
@doc """
Open the bank. Makes the account available.
"""
@spec open_bank() :: account
def open_bank() do
{:ok, pid} = GenServer.start_link(__MODULE__, [], [])
pid
end
@doc """
Close the bank. Makes the account unavailable.
"""
@spec close_bank(account) :: any
def close_bank(account) do
GenServer.stop(account)
end
@doc """
Get the account's balance.
"""
@spec balance(account) :: integer
def balance(account) do
if Process.alive?(account) do
GenServer.call(account, :balance)
else
{:error, :account_closed}
end
end
@doc """
Update the account's balance by adding the given amount which may be negative.
"""
def update(account, amount) do
if Process.alive?(account) do
GenServer.call(account, {:update, amount})
else
{:error, :account_closed}
end
end
end
Version data entries
131 entries across 131 versions & 1 rubygems