1. events reactive programming
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2. events around you tap on the shoulder traffic light goes red
turn head, say “hello”, shake hand
traffic light goes red
hit the brakes
hear cool song
dance, sing
►find 3 more events and reactions around you

3. events in phone
special action triggered by sensors or media player state
shaking, orientation change
active song changed, player paused, resumed
reacts by running the event code,
i.e. executes the actions associated to the event

4. execution model
events run to completion before another event starts running
events (and actions) never interleave
scripts with events automatically enter an event loop (“gameloop”) when an action started by the user ends
to stop the event loop, use time→stop
user can stop script as well ✿

5. gameloop event that triggers every 50ms update the state of a game
board : Board // a global board variable event gameloop …
board →evolve board →update on wall

6. orientation respond to orientation changes
phone face up/down, landscape left/right
event phone face up
player→resume
event phone face down
player→pause

7. shake uses accelerometer to detect shake event shake
media→songs→random→play

8. player events active song changed notifies that a new song is playing
player state changed notifies that the player has started to play, or paused, or resumed, etc…
event active song changed
player→active song→post to wall

9. camera buttons
pressed, half-pressed, released events triggered by phone camera button

10. tap on …
tap event on wall elements
one event per element kind

11. empty space on wall
event that triggers when new space appears on the wall
typically happens when the user reaches the end of the wall content and allows to fill the wall with more data

12. title item 1 Item 2 ☀ anecdote song→post to wall
☁ (link to sample)
► an exercise
✿ a reference