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iOS Protocols in Swift Creating Flexible Objects Using Protocols Protocol Oriented Programming Part 2

Martel Storm
Martel Storm
4,157 Points

Can't get these errors to GO AWAY!

enum Direction { case up, down, left, right }

protocol Movable { func move(_ direction: Direction, by distance: Int) }

protocol Destructable { func descreaseLife(by factor: Int) }

protocol Player: Destructable { var position: Point { get set } var life: Int { get set } init(x: Int, y: Int) }

protocol Attacker { var strength: Int { get } var range: Int { get }

func attack(player: Player)

}

struct Point { let x: Int let y: Int

init(x: Int, y: Int) {
    self.x = x
    self.y = y
}

/// Returns the surrounding points in range of
/// the current one
func points(inRange range: Int = 1) -> [Point] {
    var results = [Point]()

    let lowerBoundOfXRange = x - range
    let upperBoundOfXRange = x + range

    let lowerBoundOfYRange = y - range
    let upperBoundOfYRange = y + range

    for xCoordinate in lowerBoundOfXRange...upperBoundOfXRange {
        for yCoordinate in lowerBoundOfYRange...upperBoundOfYRange {
            let coordinatePoint = Point(x: xCoordinate, y: yCoordinate)
            results.append(coordinatePoint)
        }
    }

    return results
}

}

// Enemy

class Enemy: Player, Attacker, Movable { var life: Int = 2 var position: Point var strength: Int = 5 var range: Int = 2

required init(x: Int, y: Int) {
    self.position = Point(x: x, y: y)
}

func decreaseLife(by factor: Int) {
    life -= factor
}

func attack(player: Player) {
    player.descreaseLife(by: strength)
}

func move(_ direction: Direction, by distance: Int) {
    switch direction {
    case .up: position = Point(x: position.x, y: position.y + 1)
    case .down: position = Point(x: position.x, y: position.y - 1)
    case .right: position = Point(x: position.x + 1, y: position.y)
    case .left: position = Point(x: position.x - 1, y: position.y)
    }

}

// Tower class Tower { let position: Point var range: Int = 1 var strength: Int = 1

init(x: Int, y: Int) {
    self.position = Point(x: x, y: y)
}

func fire(at enemy: Enemy) {
    if isInRange(of: enemy) {
        enemy.decreaseLife(by: strength)
        print("Gotcha")
    } else {
        print("Darn! Out of range!")
    }
}

func isInRange(of enemy: Enemy) -> Bool {
    let availablePositions = position.points(inRange: range)

    for point in availablePositions {
        if point.x == enemy.position.x && point.y == enemy.position.y {
            return true
        }
    }

    return false
}

}

1 Answer

Anthony Lafont
Anthony Lafont
17,075 Points

Hi martel,

I saw 2 errors in your code:

  • The first saying that the class enemy didn't conform to the protocol Destructable. It is just because of a typing error. You wrote "descreaseLife" instead of "decreaseLife".

  • The second: a "}" is missing in the end of the tower class.

here is the code:

enum Direction {
    case up, down, left, right
}

protocol Movable {
    func move(_ direction: Direction, by distance: Int) }

protocol Destructable {
    func decreaseLife(by factor: Int) }

protocol Player: Destructable {
    var position: Point { get set }
    var life: Int { get set }
    init(x: Int, y: Int) }

protocol Attacker {
    var strength: Int { get }
    var range: Int { get }

    func attack(player: Player)
}

struct Point {
    let x: Int
    let y: Int

    init(x: Int, y: Int) {
        self.x = x
        self.y = y
    }

    /// Returns the surrounding points in range of
    /// the current one
    func points(inRange range: Int = 1) -> [Point] {
        var results = [Point]()

        let lowerBoundOfXRange = x - range
        let upperBoundOfXRange = x + range

        let lowerBoundOfYRange = y - range
        let upperBoundOfYRange = y + range

        for xCoordinate in lowerBoundOfXRange...upperBoundOfXRange {
            for yCoordinate in lowerBoundOfYRange...upperBoundOfYRange {
                let coordinatePoint = Point(x: xCoordinate, y: yCoordinate)
                results.append(coordinatePoint)
            }
        }

        return results
    }
}

// Enemy

class Enemy: Player, Attacker, Movable {
    var life: Int = 2
    var position: Point
    var strength: Int = 5
    var range: Int = 2

    required init(x: Int, y: Int) {
        self.position = Point(x: x, y: y)
    }

    func decreaseLife(by factor: Int) {
        life -= factor
    }

    func attack(player: Player) {
        player.decreaseLife(by: strength)
    }

    func move(_ direction: Direction, by distance: Int) {
        switch direction {
        case .up: position = Point(x: position.x, y: position.y + 1)
        case .down: position = Point(x: position.x, y: position.y - 1)
        case .right: position = Point(x: position.x + 1, y: position.y)
        case .left: position = Point(x: position.x - 1, y: position.y)
        }
    }
}

    // Tower 
class Tower {
    let position: Point
    var range: Int = 1
    var strength: Int = 1

    init(x: Int, y: Int) {
        self.position = Point(x: x, y: y)
    }

    func fire(at enemy: Enemy) {
        if isInRange(of: enemy) {
            enemy.decreaseLife(by: strength)
            print("Gotcha")
        } else {
            print("Darn! Out of range!")
        }
    }

    func isInRange(of enemy: Enemy) -> Bool {
        let availablePositions = position.points(inRange: range)

        for point in availablePositions {
            if point.x == enemy.position.x && point.y == enemy.position.y {
                return true
            }
        }

        return false
    }
}

Anthony