What is the difference between copying an array and a struct in Swift?

Copying an array in Swift creates a new independent copy of all its contents. Changes in the original array do not affect the copied one, and vice versa.

Copying a struct in Swift also creates a new copy of all its properties. If the struct contains nested reference types (e.g., classes), a reference to the object is copied, not the object itself. Changes within the reference type inside the copied struct are reflected in the original.

struct Point {
    var x: Int
    var y: Int
}

// Copying a struct
var point1 = Point(x: 10, y: 20)
var point2 = point1 // Copying the struct
point2.x = 30
print(point1.x) // Will print 10 (point1 remains unchanged)

class Container {
    var value: Int
    init(value: Int) {
        self.value = value
    }
}

struct HasReference {
    var data: Container
}

// Copying a struct with a reference type
var ref1 = HasReference(data: Container(value: 100))
var ref2 = ref1 // Copying the struct
ref2.data.value = 200 // Changing the reference type inside the struct
print(ref1.data.value) // Will print 200 (change is reflected)

// Copying an array (by value)
var array1 = [1, 2, 3]
var array2 = array1 // Copying the array
array2[0] = 10
print(array1[0]) // Will print 1 (change in array2 did not affect array1)

// Copying an array containing reference types
var containers1 = [Container(value: 1), Container(value: 2)]
var containers2 = containers1 // Copying the array (references are copied)
containers2[0].value = 10 // Changing via reference in array2
print(containers1[0].value) // Will print 10 (change is reflected in array1)

Feature	Array	Struct (without reference properties)	Struct (with reference properties)
Copy principle	By value (shallow copy)	By value	By value (references are copied)
Independence of copies	Independent by content	Independent by all properties	Independent by property-values, dependent on reference properties
Deep copying	Requires explicit implementation	Naturally	Requires explicit implementation for reference properties