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Variables, Scope, Images, Sound. IM 215 - ActionScript. Legal Variable Names. may only contain letters, numbers, dollar signs and under-scores must start with a letter or underscore or a dollar sign are case-insensitive - PowerPoint PPT Presentation
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Variables, Scope, Images, Sound
IM 215 - ActionScript
Legal Variable Names•
may o
nly
con
tain
le
tters, n
um
bers,
dolla
r sign
s an
d u
nd
er-
score
s
•m
ust sta
rt with
a le
tter
or u
nd
ersco
re o
r a
dolla
r sign
•are
case
-inse
nsitiv
e
•su
ffixe
s on
you
r varia
ble
nam
es a
llow
fo
r easy
type
iden
tifica
tion w
hen
re
ad
ing
•var fi
rstNam
e_str;
•var p
rodu
cts_arra
y;
Code hints
_mc
Movie
Clip
_arra
y
Arra
y
_str Strin
g
_btn
B
utto
n
_txt
Text Fie
ld
_sound
Sound
_colo
r C
olo
r
_vid
eo
Vid
eo
• Typical variable suffixes by type:
= vs. == operatorif (sp
eed
= 1
00
) {
//chan
ges th
e v
alu
e o
f sp
eed
if (speed
==
10
0) {
//d
oes a
com
pariso
n
= se
ts a v
alu
e
==
com
pare
s a v
alu
e
Th
is is a co
mm
on
erro
r. If you
r if/wh
ile
state
men
ts are
n’t
workin
g, ch
eck th
is first.
Variable TypingStrict vs. Automatic
Most p
rog
ram
min
g
lan
gu
ag
es re
qu
ire th
at
varia
ble
s have e
xp
licit d
ata
typ
es.
Actio
nscrip
t allo
ws fo
r au
tom
atic ty
pin
g:
var fi
rstNam
e;
firstN
am
e =
“Jim”;
firstN
am
e =
“Daisy
”;tra
ce (fi
rstNam
e);
Con
ven
ien
t, bu
t use
exp
licit typ
ing
inste
ad
in
AS
3, e
.g.:
var fi
rstNam
e:S
tring
;
Global vs Local•
Varia
ble
s that ca
n b
e
acce
ssed
thro
ugh
ou
t th
e p
rogra
m a
re ca
lled
g
lob
al v
aria
ble
s.
•Varia
ble
s that a
re
acce
ssible
on
ly to
lim
ited se
ctions o
f the
pro
gra
m a
re ca
lled
lo
cal v
aria
ble
s.
•In
Flash
, all v
aria
ble
s m
ust b
e sco
ped
to o
ne
of th
e fo
llow
ing
;
•A
fun
ction
(loca
l tim
elin
e)
•Th
e m
ain
timelin
e o
r m
ovie
clip (ro
ot
varia
ble
)
Variables on different timelines
•C
reate
two d
iffere
nt sh
apes (sq
uare
, circle
) on tw
o d
iffere
nt la
yers. C
reate
an
Actio
ns La
yer, to
o.
•O
n fra
me 1
of th
e sq
uare
layer se
t som
eX
to
3
var so
meX
:Num
ber;
som
eX
= 3
;
•O
n fra
me 1
of th
e circle
layer, se
t som
eY
to 4
var so
meY:N
um
ber;
som
eY =
4;
•Pla
ce in
stance
s of th
e clip
s on fra
me 1
la
yer 1
of th
e m
ain
timelin
e a
nd n
am
e
the in
stance
s square
and circ
le
•O
n fra
me 1
of th
e A
ctions la
yer e
nte
r the
follo
win
g fra
me scrip
t
trace
(som
eX
);tra
ce (so
meY);
Test th
e m
ovie
, what h
appens?
(NaN
=>
Not A
Num
ber)
Scope Crash!•
Varia
ble
s atta
ched
to a
m
ovie
clip tim
elin
e
have sco
pe lim
ited to
th
at tim
elin
e. T
hey a
re
not d
irectly
acce
ssible
to
scripts o
n o
ther
timelin
es, su
ch a
s our
main
movie
timelin
e.
•W
hat if w
e p
lace
the
trace
state
men
ts on
fra
me 1
of th
e sq
uare
la
yer?
•N
ow
wh
at h
ap
pens
wh
en y
ou
pu
t the
trace
state
men
ts in
the circle
layer?
Scope in Functions•
Try th
is in A
ction
s:var num1:int = 30;
var num2:int = 40;
var num3:int = 50;
addIt();
function addIt():void
{var sum:int = num1 +
num2 + num3;
trace(“Sum from
inside the
function”);
}
•W
hat h
ap
pen
s wh
en
you
trace
the su
m a
fter
the a
dd
It() fun
ction
ca
ll?
Images•
Cre
ate
an
em
pty
M
ovie
Clip
:
•In
sert ->
New
Sym
bol
•G
ive it th
e n
am
e
“spotFo
rPicture
”
•The sy
mbol lo
catio
n o
n
your sta
ge is w
here
th
e u
pper le
ft of y
our
image w
ill appear
•N
am
e th
e m
ovie
clip o
n
the sta
ge
curre
ntPictu
re
•A
dd
the fo
llow
ing
AS
co
de:
•var p
ic:Loader =
new
Lo
ader();
•pic.lo
ad(n
ew
U
RLR
equest(“fi
lenam
e.
jpg”));
•cu
rrentPictu
re.a
ddC
hil
d(p
ic);
•U
se th
e sa
me co
de to
lo
ad
a n
ew
imag
e—
just
don
’t rein
itialize
the p
ic varia
ble
.
Sound Objects•
To cre
ate
the so
un
d
and
start it
var
my_in
troso
un
d:S
ou
nd
= n
ew
Sou
nd
();m
y_in
troso
un
d.lo
ad
(n
ew
U
RLR
eq
uest("so
un
ds/fi
len
am
e.m
p3
"));
var
chan
nel:S
ou
nd
Ch
an
nel;
chan
nel =
m
y_in
troso
un
d.p
lay
();
•To
stop
the so
und
chan
nel.sto
p();
•S
ee p
p. 2
96
-31
2 in
you
r book
Exercise•
Cre
ate
a p
rog
ram
that
has o
ne fra
me a
nd
fou
r d
iffere
nt b
utto
ns, S
how
Im
ag
e 1
, Sh
ow
Imag
e
2, P
lay S
ou
nd
1, P
lay
sou
nd
2.
•D
o n
ot p
lay a
sou
nd
or
show
an
imag
e in
itially.
•W
hen
the u
ser se
lects a
p
lay so
un
d b
utto
n, a
u
niq
ue so
un
d w
ill pla
y
for e
ach
bu
tton
.
•W
hen
the u
ser se
lects a
sh
ow
imag
e b
utto
n, a
u
niq
ue im
ag
e w
ill be
disp
layed
for e
ach
b
utto
n.
Sources:•
“Actio
nS
cript 3
.0 w
ith
Flash
CS
3 a
nd
Flex”
(Ch
ap
ters 3
an
d 8
) by
Web
ster, Ya
rd, a
nd
M
cSharry
•“E
ssen
tial A
ction
Scrip
t 3
.0” b
y C
olin
Moock
(O’R
eilly
)
