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Optional types either contain a value or nil
. An optional type is defined with a question mark:
var firstLetter: Character?
Optionals can be assigned to either nil
or an instance of the optional type. Its initial value will be nil unless you assign a value yourself:
var firstLetter: Character? print(firstLetter) // prints nil firstLetter = “a” print(firstLetter) // prints Optional("a")
Only optional types can be assigned to nil. If you attempt to assign a non-optional type to nil, you will get a compile-time error.
var firstLetter: Character = “a” firstLetter = nil // ERROR: nil' cannot be assigned to type 'Character'
Instructions
1.
Create a variable called hatColor
of type optional String
with an initial value of nil
.
2.
Reassign hatColor
to “blue”.
3.
Reassign hatColor
to nil.
4.
Print the value of hatColor
. The red text in the console should display some warnings letting us know that there’s more we can do to work with optionals!
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