Why can the structure declared by let be changed?

Question

In the following code, 'ptr' is a structure declared by let, but its member variable 'pointee' can be changed, why? let ptr = UnsafeMutablePointer<Int>.allocate(capacity:1) ptr.pointee = 1

Answer 1

UnsafeMutablePointer is a structure but announces

public struct UnsafeMutablePointer<Pointee> : Strideable, Hashable {

    public var pointee: Pointee { get nonmutating set }
    public subscript(i: Int) -> Pointee { get nonmutating set }

}

Here, the "nonmutating set" means that setting the property does not mutate the state of the pointer variable itself.

Therefore, a ptr.pointeenew value can be assigned, even if it ptr is a constant, and the same is true for the indexer:

let ptr = UnsafeMutablePointer<Int>.allocate(capacity:1)
ptr.pointee = 1
ptr[0] = 2

Answer 2

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Answer 3

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Answer 4

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