What are the differences between value types and reference types in Swift?

Value Types and Reference Types differ in the way data is stored and passed.

Value Types:

• Assignment creates an independent copy of the data.
• Data is stored directly at the declaration site or on the stack (for local variables).
• Structures, enumerations, and tuples are value types.

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

var p1 = Point(x: 0, y: 0)
var p2 = p1 // Creates a copy of p1
p2.x = 10

print(p1.x) // 0
print(p2.x) // 10 - p1 remains unchanged

Reference Types:

• Assignment creates a new reference to the same data.
• Data is stored on the heap, and the reference to it is stored at the declaration site or on the stack.
• Classes are reference types.

class Rect {
    var width: Int
    var height: Int

    init(width: Int, height: Int) {
        self.width = width
        self.height = height
    }
}

var r1 = Rect(width: 10, height: 20)
var r2 = r1 // r2 now references the same object as r1
r2.width = 30

print(r1.width) // 30 - r1 has changed because r2 references the same object
print(r2.width) // 30

Main differences in the table:

Characteristic	Value Types	Reference Types
Assignment	Copies data	Copies the reference
Data storage	At declaration / on the stack	On the heap (reference at declaration)
Thread safety	Thread-safe by default	Require synchronization for threads
Types	Struct, Enum, Tuple, Array, Dict	Class, Function, Closure

The choice between types depends on the task: for representing simple independent data, Value Types are preferred; for objects with shared mutable entities and inheritance, Reference Types (classes) are suitable. Using Value Types can improve performance by reducing heap load and simplifying memory management.