(NB: this was done initially for Phoenix 1.3 and I haven't updated it yet.)

phoenix

requirements

erlang
elixir
mix
phoenix

???

param maps ALWAYS have string keys

def show(conn, %{:messenger => messenger}) do  # ⛔️
def show(conn, %{"messenger" => messenger}) do # ✅

the error is:

could not find a matching HelloWeb.HelloController.show clause to process request.

PARENTHESES MATTER WITH PIPES

**(FunctionClauseError) no function clause matching in Plug.Conn.get_resp_header/2

csrf

invalid CSRF (Cross Site Request Forgery) token, make sure all requests include a valid '_csrf_token' param or 'x-csrf-token' header

mvc notes

the view renders -- the template just displays
- e.g., don't in the template do first <> last -- send in a full_name to be rendered from the view
templates belong to views belong to controllers

various

resources "/users", UserController in routes.ex -- creates the suite of stuff for a User
resources "/users", UserController, only: [:action_one, :action_two] # or except: [...]

getting going

setup

mix phx.new <app_name>, e.g., mix phx.new hello
say yes to stuff re Rebar3, dependencies, etc
cd hello
mix ecto.create -- role "postgres" does not exist

to add a new thing:

go to <app>/lib/<app>_web/router.ex
- pipeline :browser do
  - a bunch of plugs
- pipeline :api do
  - more plugs
- scope "/", HelloWeb do
  - a pipe_through :browser
  - get "/", PageController, :index ...
add a new route:
```
<method> "/<route>", <Controller>, :<action>
get "/hello", HelloController, :index
```
- <method>: the http route we are targeting
- "/<route>: the route being targeted
- <Controller>: controller whose action we will call
- :<action>: the action we want to do
"WHEN we METHOD to ROUTE, DO ACTION of the CONTROLLER"
make out new controller
1. <app>/lib/<app>_web/controllers/<Controller>.ex
2. defmodule <App>Web.<Controller> do ...
3. it needs to have the :<action> we gave it above
make a corresponding view
1. <app>/lib/<app>_web/views/<controller>_view.ex
2. defmodule <App>Web.<App>View do ...
make a folder if we need it for the new template
1. <app>/lib/<app>_web/templates/<app>/index.html.eex

eex

<%= "boop" %> will echo
<% boop() %> executes but does not render/echo.
<%= @user %> -- implies that our controller sent along some variable under 'user', ie, render conn, "boop.html", user: user -- the @ is short for assigns.user

mix commands

start server: mix phx.server
inspect routes: mix phx.routes

routing

get "/route", ...

resources

defines a suite of routes based on actions

forward

forwards to a plug
can pop through pipe_through first -- ie java filters -- you pipe_through a pipeline, as defined

plugs

transforms to the connection
module plug: init, call
function plugs: defined in a controller, plug :authenticate then defp authenticate(conn, _) do ...
plug :assign_welcome_message, "Welcome back" makes that the default for anything in this controller -- we can override it manually via assign(:message, "Eff you")
- defp assign_welcome_message(conn, msg), do: assign(conn, :message, msg) end
- if only sometimes:
```
plug :assign_welcome_message, "Hi!" when action in [:index, :show]
```

endpoints

entrance/exit for ALL requests of the application
THIS IS WHERE WE ENABLE AUTH, CORS, SUBDOMAIN
this is our web.xml
where we setup https

controllers

index - GET all
show - GET by id
new - GET form for new
create - POST data for new
edit - GET by id and display edit form
update - PUT params for 1 updated item
delete - DELETE by id
signature: def <action>(conn, %{"param_key" => param_key}) -- good to pattern match inside the signature itself to pass on simplest data
rendering
- do NOT require a view or a template
  - text conn, "Showing id #{id} -- plain text
  - json conn, %{id: id} -- json (who knew)
  - html conn, """<html> ... </html>"""
- render: render conn, "page.html", username: username
  - CONTROLLER MUST HAVE SAME ROOT NAME AS VIEW
  - VIEW MUST HAVE SAME ROOT NAME AS DIRECTORY OF TEMPLATE
  - HelloController requires HelloView
  - HelloView requires lib/hello_web/templates/hello
  - ...which must contain "page.html"

fyi: instead of

# these are equivalent
def index(conn, _params) do
    render conn, "index.html", message: "Welcome back!"
end
 
def index(conn, _params) do
    conn
    |> assign(:message, "Welcome back!")
    |> render("index.html"
end

want a different response? no problem!

def index(conn, _params) do
    conn
    |> send_resp(201, "")
end

diff layout? eyyyyyyyy!

def index(conn, _params) do
  conn
  |> put_layout("admin.html")
  |> render("index.html")
end

diff status with a render?

def index(conn, _params) do
    conn
    |> put_status(202)
    |> render("index.html"
end

compose ALL THE THINGS

def index(conn, _params) do
    conn
    |> put_status(:not_found)
    |> put_view(HelloWeb.ErrorView)
    |> render("404.html")
end

redirect!

def index(conn, _params) do
    redirect conn, to: "/redirect_test"
end

def redirect_test(conn, _params) do
    text conn, "Redirect!"
end

default error
- somewhere, MyFallbackController
- in the control we want handled: action_fallback HelloWeb.MyFallbackController
PostFinder plug

defmodule HelloWeb.PostFinder do
    use Plug
    import Plug.Conn
    
    alias Hello.Blog
    
    def init(opts), do: opts
    
    def call(conn, _) do
        case Blog.get_post(conn.params["id"]) do
            {:ok, post} ->
                assign(conn, :post, post)
            {:error, :notfound} -> 
                conn
                |> send_resp(505, "not found"
                |> halt() # this prevents the rest of the pipeline
        end
    end
end

random

assign is setAttribute ...

aleph-naught2tog/phoenix_notes.md

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