INQ241A - Day 9 Notes

Many Sprites

What if we want a game with many sprites?

Use a loop

for 0 ≤ i < 100 do
  var sprite := board→create rectangle(5 0, 50)
  sprite→set x(math→random(board→width))
  sprite→set y(math→random(board→height))
  sprite→set speed y(100)
end for

That creates many sprites, but we also need them to do something in response to events
So in on every frame add code to do something when the sprites reach the bottom of the screen
But we can’t; the variable sprite does not exist outside of the loop
It’s only a single sprite anyway, each iteration overwites the variable named sprited created the previous iteration

We need a way to remember or reference many sprites

var sprites := board→create sprite set
for 0 ≤ i < 100 do
  var sprite := board→create rectangle(5 0, 50)
  sprite→set x(math→random(board→width))
  sprite→set y(math→random(board→height))
  sprite→set speed y(100)
  sprites→add(sprite)
end for
board→on every frame do
  for each sprite2 in sprites do
    if sprite2→y > board→height then
      sprite2→set y(0)
    else do nothing end if
  end for each
end

A sprite set is a collection of sprites
Create a sprite set using the board→create sprite set function
Add sprites to it using the sprites→add function
Do something to the sprites in the sprite set using a for each loop

Quiz

socrative.com
Room name ‘INQ241’

Activity

Activity 9