Game Development Reference
In-Depth Information
}
Optionals are useful when there is a possibility that a variable will not contain a value.
One way this can happen is when you are searching for something in a collection and the
value is not found—an address in this instance. Note the exclamation mark (
!
) after the
variable in
println()
. You use this operator to unwrap the optional. If you do not un-
wrap the optional, the compiler will not recognize the type of your variable.
There is another way to unwrap an optional. Take the previous address instance. You can
use an
if
or
case
statement to store an optional's unwrapped value in a constant.
if let address = optionalAddress {
println("The number is \(address.number())")
}
Using the
if
like this automatically unwraps the optional and stores it in the constant
address
.
for Loops
Swift provides two different implementations of the
for
loop:
for-conditional-
increment
looping and
for-in
looping.
for-conditional-increment
The
for-conditional-increment
implementation of the
for
loop is the imple-
mentation you have probably used for years. This version of the
for
loop is the tradition-
al C-style loop that uses an initializer, a condition, and an incrementer separated by semi-
colons. Take a look at this loop:
var colors = ["red", "blue", "green", "black", "blue",
"orange"]
for var index = 0; index < colors.count; index++ {
println("The color is : \(colors[index])")
}
In this example, you create an array of strings representing different colors. You then use
an
Int
value named
index
to iterate over the array and print its values. We have all seen
this type of loop a million times.
