Mida tähendab mõiste Mutating programmeerimise kontekstis?

In programming, the term "mutating" refers to operations or methods that change the state of an object after they are called. In the context of iOS and Swift, mutating methods are those that can modify the properties of a structure or enumeration.

In Swift, structures and enumerations are value types by default, so for a method to modify the properties of an instance, it must be marked with the mutating keyword.

Example:

struct Point {
    var x: Int
    var y: Int

    mutating func moveBy(dx: Int, dy: Int) {
        x += dx
        y += dy
    }
}

var p = Point(x: 0, y: 0)
p.moveBy(dx: 5, dy: 3)  // now p.x == 5, p.y == 3

Thus, mutating methods allow changing the properties of a value type, which would be impossible without this keyword.