8. Dragon ADR Position Change

  • ADR - Architecture Design Records

8.1. Problem

  • Move dragon left by 10 and down by 20

8.2. Option 1

>>> dragon.move(left=10, down=20)
>>> dragon.shift(left=10, down=20)
>>> dragon.fly(left=10, down=20)

  • Good: move by relative shifting (left, right, up, down)

  • Good: encapsulation, object knows current position, state and does move

  • Good: easy .move()

  • Bad: to use-case specific .fly(), .shift()

8.3. Option 2

>>> dragon.change_position(left=10, down=20)
>>> dragon.position_change(left=10, down=20)

  • Good: move by relative shifting (left, right, up, down)

  • Good: encapsulation, object knows current position and moves

  • Bad: to complex for now .change_position(), .position_change()

8.4. Option 3

>>> dragon.move(x=10, y=20)
>>> dragon.move_to(x=10, y=20)

  • Bad: Move by setting absolute position

  • Bad: controller must know other variables, such as velocity, surface, injuries

  • Why: it differs from set_position(), that with move() you can make an animation of movement, and with set_position() it happens instantly

../_images/oop-architecture-mvc.png

8.5. Option 4

>>> dragon.move_x(10)
>>> dragon.move_y(20)

  • Good: extensible to 3D, just add another method

  • Bad: require knowledge of an API

  • Bad: Move by setting absolute position

  • Bad: controller must know other variables, such as velocity, surface, injuries

8.6. Option 5

>>> dragon.move(10, 20)
>>> dragon.move_xy(10, 20)

  • Bad: require knowledge of an API

  • Bad: Move by setting absolute position

  • Bad: controller must know other variables, such as velocity, surface, injuries

  • Bad: not extensible to 3D

8.7. Option 6

>>> dragon.move((-10, 20))
>>> dragon.move_xy((-10, 20))

  • Bad: require knowledge of an API

  • Bad: Move by setting absolute position

  • Bad: controller must know other variables, such as velocity, surface, injuries

  • Bad: not extensible to 3D

8.8. Option 7

>>> dragon.move(dx=10, dy=-20)
>>> dragon.move(horizontal=10, vertical=-20)

  • Good: encapsulation, object knows current position and moves

  • Bad: controller computes final offset

  • Bad: controller must know, right - add to x, left - subtract y

8.9. Option 8

>>> dragon.move(0, 10, 0, 20)

>>> dragon.move((0, 10, 0, 20))

>>> dragon.move([
...     (0, 10, 0, 20),
...     (0, 10, 0, 20)])

  • Good: there is only one method move() responsible for moving

  • Bad: Python has keyword arguments, so use it

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

Example:

  • move(left, right, up, down)

Problem:

  • check(True, False, True, None)

p {
  margin-top: 25px;
  margin-bottom: 75px;
  margin-right: 50px;
  margin-left: 100px;
}

p {
  margin: 25px 50px 75px 100px;  /* top, right, bottom, left */
}

p {
  margin: 25px 50px 75px;  /* top, right-left, bottom */
}

p {
  margin: 25px 50px;  /* top-bottom, right-left */
}

p {
  margin: 25px;  /* top-right-bottom-left */
}

8.10. Option 9

>>> dragon.move([
...     (10, 20),
...     (10, 15)])

  • Good: move by relative offset

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

Example:

  • move(horizontal, vertical)

8.11. Option 9

>>> dragon.move([
...     (10, 20),
...     (50, 120),
...     (5)])

  • Bad: move by setting absolute position

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

Example:

  • move(x, y)

8.12. Option 10

>>> dragon.move({'x':50, 'y':120})

>>> dragon.move([
...     {'x':10, 'y':20},
...     {'x':10, 'y':15}])

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

8.13. Option 11

>>> dragon.move({'left':50, 'down':120})

>>> dragon.move([
...     {'left':50, 'down':120},
...     {'left':50, 'right':120},
...     {'down':50}])

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

8.14. Option 12

>>> dragon.move({'dx': 10, 'dy': 20})

>>> dragon.move([
...     {'dx': -10, 'dy': 20},
...     {'dx': -10, 'dy': 0}])

>>> dragon.move([
...     {'dx': -10, 'dy': 20},
...     {'dx': -10, 'dy': 20},
...     {'dx': -10, 'dy': 20}])

  • Bad: require knowledge of an API

  • Bad: not extensible to 3D

8.15. Option 13

  • Move by setting absolute position

>>> dragon.move([
...     Point(x=10, y=20),
...     Point(x=10, y=15)])

  • Good: extensible to 3D

  • Bad: require knowledge of an API

8.16. Option 14

>>> dragon.move([
...     {'direction': 'left', 'distance': 20},
...     {'direction': 'left', 'distance': 10},
...     {'direction': 'right', 'distance': 20}])

  • Good: extensible to 3D

  • Bad: require knowledge of an API

8.17. Option 15

>>> x = dragon.x
>>> y = dragon.y
>>> dragon.move(x=x-10, y=y+20)

>>> current = dragon.position
>>> dragon.set_position(x=current.x-10, y=current.y+20)

>>> x = dragon.x - 10
>>> y = dragon.y + 20
>>> dragon.move(x=x, y=y)

>>> dragon.x -= 10
>>> dragon.y += 20

>>> dragon.position_x -= 10
>>> dragon.position_y += 20

  • Good: extensible to 3D, just add z attribute

  • Bad: encapsulation

  • Bad: require knowledge of an API

8.18. Option 16

>>> dragon.move(x=-10, y=+20)
>>> dragon.move(dx=-10, dy=+20)
>>> dragon.change_position(left=-10, down=20)

  • Good: extensible to 3D

  • Bad: business login in controller

8.19. Option 17

>>> dragon.move(direction='left', distance=20)
>>> dragon.move(direction='right', distance=5)

  • Good: explicit

  • Good: verbose

  • Good: extensible

  • Good: extensible to 3D

  • Bad: to complex for now

  • Bad: not possible to do movement in opposite directions in the same time

8.20. Option 18

>>> LEFT = 61  # keyboard key code
>>> RIGHT = 62
>>> UP = 63
>>> DOWN = 64
>>>
>>> dragon.move(direction=LEFT, distance=20)

  • Good: explicit

  • Good: verbose

  • Good: extensible

  • Bad: to chaotic

  • Bad: to complex for now

8.21. Option 19

>>> DIRECTION_LEFT = 61  # keyboard key code
>>> DIRECTION_RIGHT = 62
>>> DIRECTION_UP = 63
>>> DIRECTION_DOWN = 64
>>>
>>> dragon.move(direction=DIRECTION_LEFT, distance=20)

  • Good: explicit

  • Good: verbose

  • Good: extensible

  • Bad: less, but still chaotic

  • Bad: to complex for now

8.22. Option 19

>>> class Direction(Enum):
...     LEFT = 61
...     RIGHT = 62
...     UP = 63
...     DOWN = 64
>>>
>>>
>>> dragon.move(Direction.LEFT, distance=5)
>>> dragon.move(direction=Direction.LEFT, distance=5)

  • Good: explicit

  • Good: verbose

  • Good: extensible

  • Good: ordered

  • Bad: to complex for now

8.23. Option 20

>>> KEY_BINDING = {
...     'ARROW_UP': dragon.move_up,
...     'ARROW_DOWN': dragon.move_down,
...     'ARROW_LEFT': dragon.move_left,
...     'ARROW_RIGHT': dragon.move_right}
>>>
>>>
>>> def action(key, time):
...     return KEY_BINDING.get(key)(time)
>>>
>>>
>>> action('ARROW_UP', 5)

  • Good: explicit

  • Good: verbose

  • Good: extensible

  • Bad: to complex for now

8.24. Option 21

>>> dragon.move_left(10)
>>> dragon.move_right(10)
>>> dragon.move_upright(10)
>>> dragon.move_downright(10)
>>> dragon.move_downleft(10)
>>> dragon.move_upleft(10)
>>> dragon.move_left_down(10, 20)

Good, because:

>>> game.bind_key(Key.LEFT_ARROW, dragon.move_left)
>>> game.bind_key(Key.RIGHT_ARROW, dragon.move_right)

Bad, because:

>>> db.execute_select(SQL)
>>> db.execute_select_where(SQL)
>>> db.execute_select_order(SQL)
>>> db.execute_select_limit(SQL)
>>> db.execute_select_offset(SQL)
>>> db.execute_select_order_limit(SQL)
>>> db.execute_select_where_order_limit(SQL)
>>> db.execute_select_where_order_limit_offset(SQL)
>>> db.execute_insert(SQL)
>>> db.execute_insert_values(SQL)
>>> db.execute_alter(SQL)
>>> db.execute_alter_table(SQL)
>>> db.execute_alter_index(SQL)
>>> db.execute_create(SQL)
>>> db.execute_create_table(SQL)
>>> db.execute_create_index(SQL)
>>> db.execute_create_database(SQL)

Why not?:

>>> db.execute(SQL)

Use Case:

>>> read_csv('iris.csv', ';', 'utf-8', True)

>>> read_csv_with_encoding('iris.csv', 'utf-8')
>>> read_csv_with_delimiter('iris.csv', ';')
>>> read_csv_with_delimiter_encoding('iris.csv', ';', 'utf-8')
>>> read_csv_with_delimiter_encoding_verbose('iris.csv', ';', 'utf-8', True)

>>> read_csv('iris.csv') \
...     .withEncoding('utf-8') \
...     .withDelimiter(';') \
...     .withVerbose(True)

>>> file = CSV()
>>> file.set_file('iris.csv')  # encapsulation?!
>>> file.set_encoding('utf-8')
>>> file.set_delimiter(';')
>>> file.set_verbose(True)

>>> read_csv('iris.csv', encoding='utf-8', delimiter=';', verbose=True)

>>> read_csv('iris.csv',
...          encoding='utf-8',
...          delimiter=';',
...          verbose=True)

  • Bad: not extensible

  • Bad: to complex for now

8.25. Decision

>>> dragon.move(left=10, down=20)

  • Good: easy

  • Good: verbose

  • Good: extensible (easy to convert to 3D)

Alternative, maybe in future:

>>> dragon.change_position(left=10, down=20)

  • Good: consistent with set_position() and get_position()

  • Good: verbose

  • Good: extensible

  • Bad: to complex for now