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I am not able to use UnsafeMutablePointer to refer to a Struct variable in Swift. Look at this playground example:

import Cocoa
var set: Set<Int> = []
let pointer = UnsafeMutablePointer<Set<Int>>.allocate(capacity: 1)
pointer.initialize(to: set)
pointer.pointee.insert(1)
Swift.print(set)

the output is [] while I expected [1]. What am I missing?

BONUS QUESTION: should I explicitly deinitialize the pointer after the usage?

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    Set is a value type. set and pointer.pointee are independent values. Adding an element to the latter does not change the former. Commented Dec 7, 2016 at 14:36
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    What do you need the reference for? You can "box" a value in a reference type (class), or pass it as inout argument to functions. More context would b e helpful. Commented Dec 7, 2016 at 14:44
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    There is also withUnsafeMutablePointer(to: &set) { ... } which calls the closure with a pointer to the value. But that pointer is only valid inside the closure. Generally Swift allows the creation of pointers to values only in a controlled scope which guarantees the lifetime of the pointed-to value. Commented Dec 7, 2016 at 14:50
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    Here is a remotely related question for arrays: stackoverflow.com/questions/28796288/…. Commented Dec 7, 2016 at 14:53
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    The nested function with an inout parameter is likely the most Swift-like way to do this. There is a reason Swift puts "Unsafe" in those type names; they're discouraged and exist mostly for compatibility with C, not for general use. Commented Dec 7, 2016 at 14:57
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