swift memory review

documentation.md

• arrays and variable-size collections use copy-on-write optimization
• multiple copies of an array share the same storage

documentationSamples.swift

// from documentation
// most cases memory is stored contiguously

// remember! in swift these are structs, copying is treated as such
// it's easy to trip this up if you are tired =D

// integer type with reference seamntics
// Arrays, like all variable-size collections in the standard library, use copy-on-write optimization. Multiple copies of an array share the same storage until you modify one of the copies. When that happens, the array being modified replaces its storage with a uniquely owned copy of itself, which is then modified in place. Optimizations are sometimes applied that can reduce the amount of copying.

class IntegerReference {
    var value = 10
}

var firstInts = [IntegerReference(), IntegerReference()]
var secondInts = firstInts

// modifications of an instance are visible to each array

firstInts[0].value = 100
print(secondInts[0].value)


// replacements addictiona nd removoval are still vislbe only in the modified aray

firstInts[0] = IntegerReference()
print(firstInts[0].value)