Embracing change

PHP Sount West, 17th June 2015

Transcript

1. EMBRACING CHANGE
   JAKUB ZALAS
   17th June 2015
   @jakub_zalas @jakzal
   

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5. DEFER COMMITMENT
   Decisions are hard to change if software
   components are tightly coupled.
   

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6. DEFER COMMITMENT
   We need loosely coupled and highly
   cohesive components to introduce changes
   easily.
   

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7. COUPLING &
   COHESION
   

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8. COHESION
   Cohesion describes how closely are
   elements in a module related
   

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9. c
   l
   a
   s
   s P
   a
   c
   k
   a
   g
   e
   C
   r
   a
   w
   l
   e
   r
   {
   p
   u
   b
   l
   i
   c f
   u
   n
   c
   t
   i
   o
   n c
   r
   a
   w
   l
   (
   )
   {
   $
   c
   h = c
   u
   r
   l
   _
   i
   n
   i
   t
   (
   )
   ;
   c
   u
   r
   l
   _
   s
   e
   t
   o
   p
   t
   (
   $
   c
   h
   , C
   U
   R
   L
   O
   P
   T
   _
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   L
   , '
   h
   t
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   p
   :
   /
   /
   a
   c
   m
   e
   .
   c
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   m
   /
   '
   )
   ;
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   u
   r
   l
   _
   s
   e
   t
   o
   p
   t
   (
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   c
   h
   , C
   U
   R
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   E
   T
   U
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   N
   T
   R
   A
   N
   S
   F
   E
   R
   , 1
   )
   ;
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   r
   e
   s
   p
   o
   n
   s
   e = c
   u
   r
   l
   _
   e
   x
   e
   c
   (
   $
   c
   h
   )
   ;
   c
   u
   r
   l
   _
   c
   l
   o
   s
   e
   (
   $
   c
   h
   )
   ;
   /
   / @
   t
   o
   d
   o e
   x
   t
   r
   a
   c
   t d
   e
   t
   a
   i
   l
   s f
   r
   o
   m t
   h
   e r
   e
   s
   p
   o
   n
   s
   e .
   .
   .
   }
   }
   

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10. SINGLE RESPONSIBILITY PRINCIPLE
    A module should have one reason to
    change.
    

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11. SINGLE RESPONSIBILITY PRINCIPLE
    Gather together the things that change for
    the same reasons.
    Separate those things that change for
    different reasons.
    http://blog.8thlight.com/uncle-bob/2014/05/08/SingleReponsibilityPrinciple.html
    

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13. COUPLING
    Modules are coupled if changing one of
    them requires changing another one.
    Martin Fowler
    http://martinfowler.com/ieeeSoftware/coupling.pdf
    

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14. COUPLING
    

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15. COUPLING THROUGH A PROPERTY
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
    r
    ;
    c
    l
    a
    s
    s C
    r
    a
    w
    l
    e
    r
    {
    /
    *
    *
    * @
    v
    a
    r B
    r
    o
    w
    s
    e
    r
    *
    /
    p
    r
    i
    v
    a
    t
    e $
    b
    r
    o
    w
    s
    e
    r
    ;
    }
    

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16. COUPLING THROUGH A METHOD CALL
    c
    l
    a
    s
    s C
    r
    a
    w
    l
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    c
    ;
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    u
    b
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    n
    c
    t
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    o
    n c
    r
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    w
    l
    (
    $
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    r
    l
    )
    {
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    h
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    s
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    c
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    e
    t
    B
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    w
    s
    e
    r
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    )
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    g
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    t
    (
    $
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    r
    l
    )
    ;
    }
    }
    

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17. COUPLING THROUGH A REFERENCE
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
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    ;
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    a
    s
    s C
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    a
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    l
    e
    r
    {
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    a
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    , B
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    w
    s
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    r $
    b
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    {
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    s
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    >
    g
    e
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    (
    $
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    ;
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18. COUPLING THROUGH A REFERENCE
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
    r
    ;
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    a
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    s C
    r
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    w
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    r
    {
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    * @
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    u
    r
    n B
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    w
    s
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    r
    *
    /
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    (
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    {
    /
    / .
    .
    .
    r
    e
    t
    u
    r
    n $
    b
    r
    o
    w
    s
    e
    r
    ;
    }
    }
    

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19. COUPLING THROUGH AN IMPLEMENTATION /
    EXTENSION
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
    r
    ;
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    s C
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    a
    w
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    e
    r e
    x
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    d
    s B
    r
    o
    w
    s
    e
    r
    {
    p
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    b
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    (
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    g
    e
    t
    (
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    r
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    ;
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20. INCREASING COHESION
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
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    a
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    _
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    c
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    r $
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    p
    u
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    (
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    g
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    t
    (
    '
    /
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    )
    ;
    /
    / .
    .
    .
    }
    }
    

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21. View Slide

22. View Slide

23. View Slide

24. Count dependencies
    c
    l
    a
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    s P
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    > $
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    ;
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25. View Slide

26. THE DEPENDENCY
    INVERSION PRINCIPLE
    

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27. HIGH-LEVEL MODULES SHOULD NOT DEPEND
    ON LOW-LEVEL MODULES.
    u
    s
    e B
    u
    z
    z
    \
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    o
    w
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    l
    a
    s
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    a
    c
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    a
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    c
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    i
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    n _
    _
    c
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    s
    t
    r
    u
    c
    t
    (
    B
    r
    o
    w
    s
    e
    r $
    b
    r
    o
    w
    s
    e
    r
    )
    {
    $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r = $
    b
    r
    o
    w
    s
    e
    r
    ;
    }
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n c
    r
    a
    w
    l
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    {
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    r
    e
    s
    p
    o
    n
    s
    e = $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r
    -
    >
    g
    e
    t
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    ;
    /
    / .
    .
    .
    }
    }
    

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28. HIGH-LEVEL MODULES SHOULD NOT DEPEND
    ON LOW-LEVEL MODULES.
    

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29. BOTH SHOULD DEPEND ON ABSTRACTIONS.
    

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30. BOTH SHOULD DEPEND ON ABSTRACTIONS.
    i
    n
    t
    e
    r
    f
    a
    c
    e H
    t
    t
    p
    C
    l
    i
    e
    n
    t
    {
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n g
    e
    t
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    ;
    }
    

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31. BOTH SHOULD DEPEND ON ABSTRACTIONS.
    c
    l
    a
    s
    s P
    a
    c
    k
    a
    g
    e
    C
    r
    a
    w
    l
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    h
    t
    t
    p
    C
    l
    i
    e
    n
    t
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    H
    t
    t
    p
    C
    l
    i
    e
    n
    t $
    h
    t
    t
    p
    C
    l
    i
    e
    n
    t
    )
    {
    $
    t
    h
    i
    s
    -
    >
    h
    t
    t
    p
    C
    l
    i
    e
    n
    t = $
    h
    t
    t
    p
    C
    l
    i
    e
    n
    t
    ;
    }
    p
    u
    b
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    c f
    u
    n
    c
    t
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    o
    n c
    r
    a
    w
    l
    (
    )
    {
    $
    r
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    s
    p
    o
    n
    s
    e = $
    t
    h
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    -
    >
    h
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    t
    p
    C
    l
    i
    e
    n
    t
    -
    >
    g
    e
    t
    (
    '
    /
    '
    )
    ;
    /
    / @
    t
    o
    d
    o p
    a
    r
    s
    e
    }
    }
    

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32. BOTH SHOULD DEPEND ON ABSTRACTIONS.
    

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33. BOTH SHOULD DEPEND ON ABSTRACTIONS.
    u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
    r
    ;
    c
    l
    a
    s
    s B
    u
    z
    z
    H
    t
    t
    p
    C
    l
    i
    e
    n
    t i
    m
    p
    l
    e
    m
    e
    n
    t
    s H
    t
    t
    p
    C
    l
    i
    e
    n
    t
    {
    p
    r
    i
    v
    a
    t
    e $
    b
    r
    o
    w
    s
    e
    r
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    B
    r
    o
    w
    s
    e
    r $
    b
    r
    o
    w
    s
    e
    r
    )
    {
    $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r = $
    b
    r
    o
    w
    s
    e
    r
    ;
    }
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n g
    e
    t
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    {
    r
    e
    t
    u
    r
    n (
    s
    t
    r
    i
    n
    g
    ) $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r
    -
    >
    g
    e
    t
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    ;
    }
    }
    

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34. ABSTRACTIONS SHOULD NOT DEPEND UPON
    DETAILS.
    

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35. DETAILS SHOULD DEPEND UPON
    ABSTRACTIONS.
    

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36. i
    n
    t
    e
    r
    f
    a
    c
    e C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r
    {
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n f
    e
    t
    c
    h
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    ;
    }
    

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37. c
    l
    a
    s
    s P
    a
    c
    k
    a
    g
    e
    C
    r
    a
    w
    l
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    c
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r $
    p
    r
    o
    v
    i
    d
    e
    r
    )
    {
    $
    t
    h
    i
    s
    -
    >
    c
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r = $
    p
    r
    o
    v
    i
    d
    e
    r
    ;
    }
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n c
    r
    a
    w
    l
    (
    )
    {
    $
    c
    o
    n
    t
    e
    n
    t = $
    t
    h
    i
    s
    -
    >
    c
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r
    -
    >
    f
    e
    t
    c
    h
    (
    '
    /
    '
    )
    ;
    /
    / @
    t
    o
    d
    o p
    a
    r
    s
    e
    }
    }
    

    View Slide

38. u
    s
    e B
    u
    z
    z
    \
    B
    r
    o
    w
    s
    e
    r
    ;
    c
    l
    a
    s
    s B
    u
    z
    z
    C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r i
    m
    p
    l
    e
    m
    e
    n
    t
    s C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    b
    r
    o
    w
    s
    e
    r
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    B
    r
    o
    w
    s
    e
    r $
    b
    r
    o
    w
    s
    e
    r
    )
    {
    $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r = $
    b
    r
    o
    w
    s
    e
    r
    ;
    }
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n f
    e
    t
    c
    h
    (
    )
    {
    r
    e
    t
    u
    r
    n (
    s
    t
    r
    i
    n
    g
    ) $
    t
    h
    i
    s
    -
    >
    b
    r
    o
    w
    s
    e
    r
    -
    >
    g
    e
    t
    (
    '
    /
    '
    )
    ;
    }
    }
    

    View Slide

39. View Slide

40. View Slide

41. u
    s
    e G
    u
    z
    z
    l
    e
    \
    C
    l
    i
    e
    n
    t
    ;
    c
    l
    a
    s
    s G
    u
    z
    z
    l
    e
    C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r i
    m
    p
    l
    e
    m
    e
    n
    t
    s C
    o
    n
    t
    e
    n
    t
    P
    r
    o
    v
    i
    d
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    g
    u
    z
    z
    l
    e
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    C
    l
    i
    e
    n
    t $
    g
    u
    z
    z
    l
    e
    )
    {
    $
    t
    h
    i
    s
    -
    >
    g
    u
    z
    z
    l
    e = $
    g
    u
    z
    z
    l
    e
    ;
    }
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n f
    e
    t
    c
    h
    (
    $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    {
    $
    r
    e
    q
    u
    e
    s
    t = $
    t
    h
    i
    s
    -
    >
    g
    u
    z
    z
    l
    e
    -
    >
    c
    r
    e
    a
    t
    e
    R
    e
    q
    u
    e
    s
    t
    (
    '
    G
    E
    T
    '
    , $
    r
    e
    s
    o
    u
    r
    c
    e
    )
    ;
    $
    r
    e
    s
    p
    o
    n
    s
    e = $
    r
    e
    q
    u
    e
    s
    t
    -
    >
    s
    e
    n
    d
    (
    )
    ;
    r
    e
    t
    u
    r
    n $
    r
    e
    s
    p
    o
    n
    s
    e
    -
    >
    g
    e
    t
    B
    o
    d
    y
    (
    )
    ;
    }
    }
    

    View Slide

42. View Slide

43. What about the framework?
    c
    l
    a
    s
    s P
    r
    o
    d
    u
    c
    t
    C
    o
    n
    t
    r
    o
    l
    l
    e
    r e
    x
    t
    e
    n
    d
    s C
    o
    n
    t
    r
    o
    l
    l
    e
    r
    {
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n s
    e
    a
    r
    c
    h
    A
    c
    t
    i
    o
    n
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    {
    $
    p
    r
    o
    d
    u
    c
    t
    s = $
    t
    h
    i
    s
    -
    >
    g
    e
    t
    (
    '
    d
    o
    c
    t
    r
    i
    n
    e
    '
    )
    -
    >
    g
    e
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    (
    '
    A
    c
    m
    e
    :
    P
    r
    o
    d
    u
    c
    t
    '
    )
    ;
    -
    >
    s
    e
    a
    r
    c
    h
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    ;
    r
    e
    t
    u
    r
    n $
    t
    h
    i
    s
    -
    >
    r
    e
    n
    d
    e
    r
    (
    '
    p
    r
    o
    d
    u
    c
    t
    /
    s
    e
    a
    r
    c
    h
    .
    h
    t
    m
    l
    .
    t
    w
    i
    g
    '
    ,
    [
    '
    p
    r
    o
    d
    u
    c
    t
    s
    ' =
    > $
    p
    r
    o
    d
    u
    c
    t
    s
    ]
    )
    ;
    }
    }
    

    View Slide

44. View Slide

45. i
    n
    t
    e
    r
    f
    a
    c
    e P
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    {
    /
    *
    *
    * @
    r
    e
    t
    u
    r
    n P
    r
    o
    d
    u
    c
    t
    [
    ]
    *
    /
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n s
    e
    a
    r
    c
    h
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    ;
    }
    

    View Slide

46. c
    l
    a
    s
    s D
    o
    c
    t
    r
    i
    n
    e
    P
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y i
    m
    p
    l
    e
    m
    e
    n
    t
    s P
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    {
    p
    r
    i
    v
    a
    t
    e $
    e
    m
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    E
    n
    t
    i
    t
    y
    M
    a
    n
    a
    g
    e
    r $
    e
    m
    )
    {
    $
    t
    h
    i
    s
    -
    >
    e
    m = $
    e
    m
    ;
    }
    /
    *
    *
    * @
    r
    e
    t
    u
    r
    n P
    r
    o
    d
    u
    c
    t
    [
    ]
    *
    /
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n s
    e
    a
    r
    c
    h
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    {
    r
    e
    t
    u
    r
    n $
    t
    h
    i
    s
    -
    >
    e
    m
    -
    >
    c
    r
    e
    a
    t
    e
    Q
    u
    e
    r
    y
    B
    u
    i
    l
    d
    e
    r
    (
    )
    -
    >
    s
    e
    l
    e
    c
    t
    (
    '
    p
    '
    )
    -
    >
    f
    r
    o
    m
    (
    P
    r
    o
    d
    u
    c
    t
    :
    :
    c
    l
    a
    s
    s
    , '
    p
    '
    )
    -
    >
    w
    h
    e
    r
    e
    (
    '
    p
    .
    t
    i
    t
    l
    e L
    I
    K
    E :
    k
    e
    y
    w
    o
    r
    d
    s
    '
    )
    -
    >
    s
    e
    t
    P
    a
    r
    a
    m
    e
    t
    e
    r
    (
    '
    k
    e
    y
    w
    o
    r
    d
    s
    '
    , '
    %
    '
    .
    $
    k
    e
    y
    w
    o
    r
    d
    s
    .
    '
    %
    '
    )
    -
    >
    g
    e
    t
    Q
    u
    e
    r
    y
    (
    )
    -
    >
    g
    e
    t
    R
    e
    s
    u
    l
    t
    (
    )
    ;
    }
    }
    

    View Slide

47. c
    l
    a
    s
    s P
    r
    o
    d
    u
    c
    t
    C
    o
    n
    t
    r
    o
    l
    l
    e
    r
    {
    p
    r
    i
    v
    a
    t
    e $
    p
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    ;
    p
    r
    i
    v
    a
    t
    e $
    t
    e
    m
    p
    l
    a
    t
    i
    n
    g
    ;
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n _
    _
    c
    o
    n
    s
    t
    r
    u
    c
    t
    (
    P
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y $
    p
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    ,
    E
    n
    g
    i
    n
    e
    I
    n
    t
    e
    r
    f
    a
    c
    e $
    t
    e
    m
    p
    l
    a
    t
    i
    n
    g
    ) {
    $
    t
    h
    i
    s
    -
    >
    p
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y = $
    p
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    ;
    $
    t
    h
    i
    s
    -
    >
    t
    e
    m
    p
    l
    a
    t
    i
    n
    g = $
    t
    e
    m
    p
    l
    a
    t
    i
    n
    g
    ;
    }
    /
    / .
    .
    .
    }
    

    View Slide

48. c
    l
    a
    s
    s P
    r
    o
    d
    u
    c
    t
    C
    o
    n
    t
    r
    o
    l
    l
    e
    r
    {
    /
    / .
    .
    .
    p
    u
    b
    l
    i
    c f
    u
    n
    c
    t
    i
    o
    n s
    e
    a
    r
    c
    h
    A
    c
    t
    i
    o
    n
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    {
    $
    p
    r
    o
    d
    u
    c
    t
    s = $
    t
    h
    i
    s
    -
    >
    p
    r
    o
    d
    u
    c
    t
    R
    e
    p
    o
    s
    i
    t
    o
    r
    y
    -
    >
    s
    e
    a
    r
    c
    h
    (
    $
    k
    e
    y
    w
    o
    r
    d
    s
    )
    ;
    r
    e
    t
    u
    r
    n $
    t
    h
    i
    s
    -
    >
    t
    e
    m
    p
    l
    a
    t
    i
    n
    g
    -
    >
    r
    e
    n
    d
    e
    r
    R
    e
    s
    p
    o
    n
    s
    e
    (
    '
    p
    r
    o
    d
    u
    c
    t
    /
    s
    e
    a
    r
    c
    h
    .
    h
    t
    m
    l
    .
    t
    w
    i
    g
    '
    ,
    [
    '
    p
    r
    o
    d
    u
    c
    t
    s
    ' =
    > $
    p
    r
    o
    d
    u
    c
    t
    s
    ]
    )
    ;
    }
    }
    

    View Slide

49. View Slide

50. View Slide

51. View Slide

52. View Slide

53. Good code doesn't take more time to write.
    What takes a lot of time is the learning how
    to write good code.
    

    View Slide

54. THANK YOU!
    @jakub_zalas @jakzal
    

    View Slide