This content originally appeared on flaviocopes.com and was authored by flaviocopes.com
This tutorial belongs to the Swift series
Optionals are one key feature of Swift.
When you don’t know if a value will be present or absent, you declare the type as an optional.
The optional wraps another value, with its own type. Or maybe not.
We declare an optional adding a question mark after its type, like this:
var value: Int? = 10Now value is not an Int value. It’s an optional wrapping an Int value.
To find out if the optional wraps a value, you must unwrap it.
We do so using an exclamation mark:
var value: Int? = 10
print(value!) //10Swift methods often return an optional. For example the Int type initializer accepts a string, and returns an Int optional:
This is because it does not know if the string can be converted to a number.
If the optional does not contain a value, it evaluates as nil, and you cannot unwrap it:
nil is a special value that cannot be assigned to a variable. Only to an optional:
You typically use if statements to unwrap values in your code, like this:
var value: Int? = 2
if let age = value {
print(age)
}
This content originally appeared on flaviocopes.com and was authored by flaviocopes.com
flaviocopes.com | Sciencx (2021-06-07T05:00:00+00:00) Swift Optionals and `nil`. Retrieved from https://www.scien.cx/2021/06/07/swift-optionals-and-nil/
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