2
2
.
.
2
2
.
.
4
4
D
D
a
a
t
t
a
a
T
T
y
y
p
p
e
e
-
-
A
A
l
l
i
i
a
a
s
s
I
I
n
n
f
f
o
o
Data Type Aliases define an alternative name for an existing Data Type.
D
D
a
a
t
t
a
a
T
T
y
y
p
p
e
e
A
A
l
l
i
i
a
a
s
s
S
S
y
y
n
n
t
t
a
a
x
x
Data Type Alias is declared by
● using Keyword typealias
● followed by Name StreetNumber
● followed by existing Data Type Int
Example
typealias StreetNumber = Int
var address : StreetNumber = 23
