TylerPachal

/* This is a small example of how to use Play! Json to validate a JsValue, when you need to consider a combination
 * of fields.  In this example, I have ContactInfo, where either a phone number or an email address have to provided
 * (or both).  Each field is represented as a simple String, when in reality you may want to do further validation
 * on each field to make sure it is a valid phone number and/or email.
 */

import play.api.libs.json._

object Main {

TylerPachal

// This is an example of how to express Infinity in Json using the Play! Scala Json library.
// Infinity cannot be expressed as a Scalar value in Json, so I am using an object to hold it instead.
//
// Example of a finite value:
//  {
//    "value": 12.009,
//    "isInfinite": false
//  }
//
// Example of an infinite value:

TylerPachal

# Create a new Parser process
iex(2)> {:ok, pid} = Parser.start_link()
{:ok, #PID<0.118.0>}

# Verify the process is alive
iex(3)> Process.alive?(pid)
true

# Send it a valid message
iex(4)> GenServer.call(pid, "100")

TylerPachal

defmodule Parser do
  use GenServer
  
  def start_link() do
    GenServer.start_link(__MODULE__, :ok, [])
  end
  
  def handle_call(message, _from, state) do
    i = String.to_integer(message)
    {:reply, i, state}

TylerPachal

# Create a new Parser process
iex(1)> {:ok, pid} = Parser.start_link()
{:ok, #PID<0.112.0>}

# Figure out our iex process' PID
iex(2)> self()
#PID<0.110.0>

# See that our iex process is linked to the Parser process
iex(3)> Process.info(self(), :links)

TylerPachal

## lib/MySupervisor.ex
defmodule MySupervisor do
  use GenServer
  
  ## API
  def start_link(child_spec_list) do
    GenServer.start_link(__MODULE__, child_spec_list)
  end
  
  def list_processes(pid) do

TylerPachal

# Start a supervisor with two child specifications
iex(1)> {:ok, pid} = MySupervisor.start_link([{Parser, :start_link, []}, {Parser, :start_link, []}])
{:ok, #PID<0.123.0>}

# See the two processes that the supervisor started
iex(2)> MySupervisor.list_processes(pid)
%{#PID<0.124.0> => {Parser, :start_link, []},
  #PID<0.125.0> => {Parser, :start_link, []}}
  
# Verify the supervisor has linked to the processes

TylerPachal

# Get a reference to one of the Parser process pid
iex(4)> parser_pid = MySupervisor.list_processes(pid) |> Map.keys |> List.first
#PID<0.124.0>

# Send a valid message
iex(5)> GenServer.call(parser_pid, "100")
100

# Send an invalid message
iex(6)> GenServer.call(parser_pid, "tyler")

TylerPachal

## OTP Callbacks
def handle_info({:EXIT, dead_pid, _reason}, state) do
  
  # Start new process based on dead_pid spec
  {new_pid, child_spec} = state
  |> Map.get(dead_pid)
  |> start_child()
  
  # Remove the dead_pid and insert the new_pid with its spec
  new_state = state

TylerPachal

# Start a supervisor with two child specifications
iex(1)> {:ok, pid} = MySupervisor.start_link([{Parser, :start_link, []}, {Parser, :start_link, []}])
{:ok, #PID<0.112.0>}

# See the two processes that the supervisor started
iex(2)> MySupervisor.list_processes(pid)
%{#PID<0.113.0> => {Parser, :start_link, []},
  #PID<0.114.0> => {Parser, :start_link, []}}

# Get a reference to one of the Parser process pid