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iOS Object-Oriented Swift 2.0 Class Inheritance Overriding Methods

Eduardo Calvachi
Eduardo Calvachi
6,049 Points
Posted by Eduardo Calvachi
Eduardo Calvachi
6,049 Points

Error cannot convert value of type 'SuperEnemy' to expected argument of type 'LaserTower'

I am getting an error: Cannot convert value of type 'SuperEnemy' to expected argument of type 'LaserTower' when I try to pass in superEnemy to the fireAtEnemy method of LaserTower as described on the video. Here are my classes and subclasses, maybe I missed something:

class Enemy {
    var life: Int = 2
    var position: Point

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

    func dicreaseHealth(factor: Int){
        life -= factor
    }
}

class Tower {
    let position: Point // tower doesn't move
    var range: Int = 1
    var strength: Int = 1

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

    func fireAtEnemy(enemy: Enemy){
        if inRange(self.position, range: self.range, target: enemy.position) {
            while enemy.life > 0 {
                enemy.dicreaseHealth(self.strength)
                print("Enemy has been hit!")
            }
        } else {
            print("Enemy out of range!")
        }
    }

    func inRange(position: Point, range: Int, target: Point) -> Bool{
        let availablePositions = position.surroundingPoints(withRange: range)
        for point in availablePositions {
            if point.x == target.x && point.y == target.y {
                return true
            }
        }
        return false
    }
}

class SuperEnemy: Enemy {
    let isSuper: Bool = true

    override init(x: Int, y: Int) {
        super.init(x: x, y: y)
        self.life = 10
    }
}

class LaserTower: Tower {
    override init(x: Int, y: Int) {
        super.init(x: x, y: y)
        self.range = 100
        self.strength = 100
    }

    override func fireAtEnemy(enemy: Enemy) {
        while enemy.life > 0 {
            enemy.dicreaseHealth(self.strength)
            print("Enemy has been Vanquished!")
        }
    }
}

Class Instantiation:

let laserTower = LaserTower(x: 0, y: 0)
let superEnemy = SuperEnemy(x: 20, y: 20)

LaserTower.fireAtEnemy(superEnemy) 
//Error: cannot convert value of type 'SuperEnemy' to expected argument of type 'LaserTower'

1 Answer

Steven Deutsch
Steven Deutsch
21,046 Points
Steven Deutsch
Steven Deutsch
21,046 Points

Hey Eduardo Calvachi,

You need to change the capital "L" in LaserTower to a lowercase "l". You need to call the fireAtEnemy method on the instance of LaserTower that you assigned to your laserTower constant. 

let laserTower = LaserTower(x: 0, y: 0)
let superEnemy = SuperEnemy(x: 20, y: 20)
LaserTower.fireAtEnemy(superEnemy) 
//Error: cannot convert value of type 'SuperEnemy' to expected argument of type 'LaserTower'

// It should be
laserTower.fireAtEnemy(superEnemy)

Good Luck!

Eduardo Calvachi
Eduardo Calvachi
6,049 Points
Eduardo Calvachi
Eduardo Calvachi
6,049 Points

You're right Steven I was calling on the object rather than the instance. Thanks for finding the mistake!