Dependency Injection for beginners

Slides for my talk at the 16th PHP Belfast Meet-up.

Transcript

1. Dependency Injection
   David Frame of 31interactive
   

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2. ?
   

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3. Scenario #1
   We need to be able to test our
   order class without sending
   any emails!
   

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4. Dummy mailer class with
   a send() method that
   does nothing!
   

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5. What is dependency
   injection?
   

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7. Single Responsibility Principle
   a class should have only a single responsibility
   Open / Closed Principle
   “software entities … should be open for extension, but
   closed for modification.”
   Liskov Substitution Principle
   Interface Segregation Principle
   Dependency Inversion Principle
   one should “Depend upon Abstractions. Do not depend
   upon concretions.”
   

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8. Scenario #2
   We need to store emails in the
   database so they can be
   queued up and sent at a later
   date!
   

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12. Dependency
    Injection Containers
    

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14. Thanks for listening!
    Any questions? :)
    Email: david.grant.frame@gmail.com
    Twitter: @DaGrFr
    Review this talk at https://joind.in/16984
    

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