Certainly! Let's start by examining the provided code and then rewrite it using a mutating function.
Original Code
struct Point {
var x: Double
var y: Double
func moveBy(x deltaX: Double, y deltaY: Double) -> Point {
return Point(x: x + deltaX, y: y + deltaY)
}
}
var point = Point(x: 0.0, y: 0.0)
point = point.moveBy(x: 2.5, y: 4.5)
print("Updated point: (\(point.x), \(point.y))") // Output: Updated point: (2.5, 4.5)
Rewritten Code Using Mutating Function
To rewrite this code using a mutating function, we need to modify the moveBy method so that it directly changes the properties of the Point instance instead of returning a new instance.
struct Point {
var x: Double
var y: Double
mutating func moveBy(x deltaX: Double, y deltaY: Double) {
x += deltaX
y += deltaY
}
}
var point = Point(x: 0.0, y: 0.0)
point.moveBy(x: 2.5, y: 4.5)
print("Updated point: (\(point.x), \(point.y))") // Output: Updated point: (2.5, 4.5)
Explanation
Original Code: The moveBy method returns a new Point instance with updated coordinates, and the caller must reassign the result to the original variable.
Rewritten Code: The moveBy method is marked as mutating, allowing it to modify the properties x and y of the Point instance directly. This eliminates the need to return a new instance and reassign it.
