Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Object-Oriented Swift Classes in Swift Helper Methods

Michael Williams
PLUS
Michael Williams
Courses Plus Student 8,059 Points

code from lesson in object oriented programming not working–swift

I typed this code out word for word while doing the lesson, but I keep getting two errors on the isInRange method:

use of unresolved identifier 'position'

use of unresolved identifier 'range'

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 point.
    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)
            }
        }
        print(results)
        return results
    }
}

let coordinatePoint = Point(x: 0, y: 0)  //This creates an instance of the struct.

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

    init(x: Int, y: Int) {
        self.position = Point(x: x, y: y)
    }
    func decreaseLife(by factor: Int) {
        life -= factor
    }
}

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
    }

let tower = Tower(x: 0, y: 0)
let enemy = Enemy(x: 1, y: 1)

tower.fire(at: enemy)

2 Answers

Chris Stromberg
PLUS
Chris Stromberg
Courses Plus Student 13,389 Points

You have to include the isInRange function within your tower class!

import Foundation

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 point.
    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)
            }
        }
        print(results)
        return results
    }

}

let coordinatePoint = Point(x: 0, y: 0) //This creates an instance of the struct.

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

    init(x: Int, y: Int) {
        self.position = Point(x: x, y: y)
    }
    func decreaseLife(by factor: Int) {
        life -= factor
    }

}

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
    }
}
let tower = Tower(x: 0, y: 0)
let enemy = Enemy(x: 1, y: 1)

tower.fire(at: enemy)
Chris Stromberg
PLUS
Chris Stromberg
Courses Plus Student 13,389 Points

Also to add code formatted for swift do this....

Wrap your code with 3 backticks (```) on the line before and after. If you specify the language after the first set of backticks, that'll help us with syntax highlighting.

    ```swift
    Your code here....
   ```