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Addison Francisco
9,561 PointsProtocol Oriented Programming Part 2: The pasted code for Point struct is conflicting with the Enemy class
Still getting the hang of OOP and wanted some clarification. In the video, Pasan pastes some code from a previous course "Object-Oriented Swift" that declares a struct named Point
struct Point {
let x: Int
let y: Int
init(x: Int, y: Int) {
self.x = x
self.y = y
}
func surroundingPoints(withRange range: Int = 1) -> [Point] {
var results: [Point] = []
for xCoord in (x-range)...(x+range) {
for yCoord in (y-range)...(y+range) {
let coordinatePoint = Point(x: xCoord, y: yCoord)
results.append(coordinatePoint)
}
}
return results
}
}
Point's x and y properties are declared as constants in that previous course, but in this video we declare a protocol with a property of type Point that is gettable and settable.
protocol PlayerType {
var position: Point { get set }
var life: Int { get set }
init(point: Point)
}
Since Enemy adopts the PlayerType protocol This is causing an error in the switch statement in Enemy class's move() method that says Left side of mutating operator isn't mutable: 'y' is a 'let' constant
func move(direction: Direction, distance: Int) {
switch direction {
case .Up: position.y += 1
case .Down: position.y -= 1
case .Left: position.x -= 1
case .Right: position.x += 1
}
}
I came to the conclusion that I just needed to modify the Point struct's stored properties to be variables since we are defining a protocol that declares the property requirements of Point should be gettable and settable. Am I missing anything here?
2 Answers
JT Keller
12,731 PointsAddison - I used the same approach in regards to refactoring the constants as variables.
Also I'd like to note that var parameters are being deprecated as of Swift 3.0, so I addressed this issue for the attach function by using shadowing as seen below.
If needed here's the information related to the change: https://github.com/apple/swift-evolution/blob/master/proposals/0003-remove-var-parameters.md
func attack(player: PlayerType) {
var player = player
player.life = player.life - strength
}
John Carty
6,444 PointsYou actually need to modify the Point that is member of the Player class.
Your method should look something like:
case "Up": position = Point(position.x+1, position.y)
syntax may be a bit off, I am coding from memory without access to Xcode.
Addison Francisco
9,561 PointsI actually downloaded the Project File and saw that he did what I did as well. Seems like an oversight.
struct Point {
// Code in the video that was causing errors
// let x: Int
// let y: Int
// Code in the Project File that resolved errors
var x: Int
var y: Int
init(x: Int, y: Int) {
self.x = x
self.y = y
}
func surroundingPoints(withRange range: Int = 1) -> [Point] {
var results: [Point] = []
for xCoord in (x-range)...(x+range) {
for yCoord in (y-range)...(y+range) {
let coordinatePoint = Point(x: xCoord, y: yCoord)
results.append(coordinatePoint)
}
}
return results
}
}