Swift Viewing Variable Memory Addresses

withUnsafePointer

Let's not talk. Let's put the code first.

        withUnsafeBufferPointer(to: a) { point in
            let address = UnsafeRawPointer(point)
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
        }

validate (a theory)copy on write

The assignment of value types will copy the object, and for some containers, Ago has done in order to avoid the performance loss caused by the copying of Array and Set, willcopy on writeThe mechanisms are optimized.

For Array, Dictionary, and Set types, no copy occurs when they are assigned, only after they are modified.

When we validate with the code, after trying to use thewithUnsafePointerWhen you assign a value to an array, you will find that the address of the two variables will be different. Of course, this is reasonable, after all, after the assignment of the value type, the two variables should be independent of each other in memory.
To validate the COW, Array gives us another method, which is thewithUnsafeBufferPointerIf you use this method to view the array after the assignment, you will see that the address of the output is unchanged.
as a matter of factwithUnsafeBufferPointerThe address pointed to is the memory address at which the array stores the data.withUnsafePointerPointed.

Code Example

        var array1 = [1, 2, 3]
         { point in
            let address = !
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 105553141216992
        }
        withUnsafePointer(to: array1) { point in
            let address = UnsafeRawPointer(point)
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 6089438336
        }
        var array2 = array1 // The data is not really copied here，Instead, it's shared memory.
         { point in
            let address = !
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 105553141216992
        }
        withUnsafePointer(to: array2) { point in
            let address = UnsafeRawPointer(point)
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 6089438320
        }
        array2[2] = 1
         { point in
            let address = !
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 105553141218080
        }
        withUnsafePointer(to: array2) { point in
            let address = UnsafeRawPointer(point)
            let addressInt = Int(bitPattern: address)
            print("\(addressInt)")
            // 6089438280
        }