I'm reading Apple's developer documentation on Optional Binding
Why can't I use:
if someOptional? {
statements
}
Instead of
if let constantName = someOptional {
statements
}
Why when there is no need for a local variable or constant?
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1you use optional binding when you want value from the optional...not just check if the optional value contains value or nil – LC 웃 May 02 '16 at 18:38
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2you can always do `if someOptional != nil {` or if you don't need the unwrapped value you can also do `if let _ = someOptional {` – Ozgur Vatansever May 02 '16 at 18:38
2 Answers
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Why can't I use: if someOptional? {...}
Because the ? suffix on an optional variable is reserved for optional chaining, which allows you to access a property or call a method on a given optional variable. For example:
// returns an optional version of a given property
let aProperty = anOptional?.someProperty
// calls the method if aProperty contains a value – otherwise doesn't
aProperty?.doSomething()
If you just want to check whether an optional contains a value, but don't care about that underlying value, you can simply compare it with nil. For example:
if anOptional != nil {
// do something
}
Hamish
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If you're interested, I co-wrote [an answer here](http://stackoverflow.com/questions/32170456/what-does-fatal-error-unexpectedly-found-nil-while-unwrapping-an-optional-valu) that lists (almost) all the ways of safely working with optionals – although the Apple Swift docs are hard to beat! – Hamish May 02 '16 at 19:28
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The simple answer is that someOptional is an Optional, whereas constantName is a Type.
An Optional is not simply the state of a variable, it's an entirely different type. If you were to set var someOptional: String? to var someOptional: String, you're not unwrapping someOptional, you're actually changing the type of someOptional.
It's functionally the same as changing var someOptional: String to var someOptional: Int
GetSwifty
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