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What  does  it  mean  to  YOU?

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How  do  YOU  use  it  today?

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How  would  YOU  like  to  use  it  tomorrow?

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A  Journey  …. How  to  make  "changing  a  username"  complex  …

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Let's  go  back  in  time

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Question  :   How  can  we Improve  the  code  structure  ?

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Achievement  unlocked! HEXAGONAL  DESIGN

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Question  :   Where  do  we  place the  controller  ?

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Question  :   Where  will  we  change the  userName?

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Question  :   How  can  the  controller change  the  userName?

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ChangeUsername Command COMMAND  BUS ChangeUsername Command  Handler

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Achievement  unlocked! THE  COMMAND  PATTERN

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COMMAND  BUS (Multiplexer) ChangeUsername Command  Handler FireEmployee Command  Handler GrantBonus Command  Handler ChangeUsername Command

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Achievement  unlocked! THE  SERVICE  LAYER

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Question  :   Where  do  we  place the  command?

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Question  :   Where  do  we  place  the command  handler?

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Question  :   Where  do  we  place  the command  bus?

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Achievement  unlocked! THE  BRIDGE  PATTERN

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Achievement  unlocked! THE  REPOSITORY  PATTERN

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Database UserRepository UserRepository Interface InMemory UserRepository CSV UserRepository

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Achievement  unlocked! INVERSION  OF  CONTROL  PATTERN

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Question  :   Where  do  we  place repositories?

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Question  :   What  if  we  wanted  to cache  data?

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Database UserRepository UserRepository Interface Caching UserRepository

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Achievement  unlocked! THE  DECORATOR  PATTERN

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Question  :   Where  do  we  place  the validation?

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ChangeUsername Command COMMAND  BUS ChangeUsername Command  Handler Validation Middleware

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Achievement  unlocked! THE  MIDDLEWARE  PATTERN

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UserNameExists Rule Symfony UserNameAllowed Constraint CommandBus SymfonyValidator Middleware UserNameContains NoSwearWords Rule

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Question  :   Where  do  we  place  the logging?

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ChangeUsername Command COMMAND  BUS ChangeUsername Command  Handler Validation Middleware Logger Middleware

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Question  :   Where  do  we  place  the Security  voters?

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ChangeUsername Command COMMAND  BUS ChangeUsername Command  Handler Security Middleware Logger Middleware Validator Middleware

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UserIsBlocked Rule Symfony Change UserName Voter CommandBus SymfonySecurity Middleware UserIsOwner Rule

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Question  :   Where  do  we  place  the emailing?

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Question  :   Where  do  we  place  the event  dispatcher?

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Question  :   Where  do  we  place  the event?

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Achievement  unlocked! THE  DOMAIN  EVENT

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Question  :   Where  do  we  place  the event  listeners?

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Achievement  unlocked! THE  OBSERVER  PATTERN

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Question  :   What  if  we  needed  to sync  the  user?

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Domain Models 3rd Party System Adapter Transformations

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Achievement  unlocked! THE  ADAPTER  PATTERN

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Question  :   Dude  …  you  are  very  optimistic  about  the   connection How  can  we  log  stuff?

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SomeCrm\Client ::syncUser() HTTP  /  SOAP  Client SOME  CRM SERVER Logger Middleware

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Question  :   That  is  ok,  but  what  about ACTUAL  error  handling?

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Question  :   Syncing  can  be  so  SLOOOW What  can  we  do  about  it?

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ASYNC COMMAND  BUS ASYNC EVENT  DISPATCHER ASYNC HANDLER  /  LISTENER JOBS  Monitor Message  Queue ASYNC LISTENER

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Question  :   How  can  we  handle  urgent  exceptions?

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Level Urgency Notification Debug / / Info / / Notice / / Warning / / Error 1d / Critical 2-­‐4h Push Alert 2h Push Emergency <1h Push

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Question  :   How  do  we  handle  errors?

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https://github.com/phpro/api-­‐problem https://github.com/phpro/api-­‐problem-­‐bundle

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Positive: • Every  function  does  1  thing • Every  class  does  1  thing • Easy  to  test • Easy  to  debug • Easy  to  extend Negative: • We  made  a  simple  task   complex  (but  not  really) • It  takes  a  lot  of  boilerplate   code • You  have  to  know  what  you   are  doing!

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Question  :   How  do  we Fetch  data?

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Question  :   How  do  we  handle Critical  Business  Rules?

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Example  :   The  total  price  of  an  invoice is  20  EUR  per  invoiced  items.

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Example  :   total  =  20  *  count(invoice.items)

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Achievement  unlocked! PURE  FUNCTIONS

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Next  feature  request:   Please  make  it  25  EUR  per  invoice  line! Ah  yea:  only  the  even  lines  count

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Achievement  unlocked! FUNCTION  COMPOSITION

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Next  feature  request:   When  an  invoice  is  created We  want  to  log  some  statistics

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Achievement  unlocked! IMMUTABILITY

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