Swift Xcode Error: Cannot Convert Value of Type

Question

Sorry, I'm a noob at Swift and still learning.

I'm getting the following error message from Xcode for the following swift code: "Cannot convert value of type 'Town?.Type' (aka 'Optional.Type') to expected argument type 'Town?'"

class Vampire: Monster { var vampirePopulation: [Vampire] = [] override func terrorizeTown() { if town?.population > 1 { town?.changePopulation(-1) } else { town?.population = 0 } vampirePopulation.append(Vampire(town: Town?, monsterName: String)) print("\(vampirePopulation.count) vampires") super.terrorizeTown() } }

Here is the Monster Class:

import Foundation class Monster { static let isTerrifying = true class var spookyNoise: String { return "Grrr" } var town: Town? var name = String () var victimPool: Int { get { return town?.population ?? 0 } set(newVictimPool) { town?.population = newVictimPool } } init(town: Town?, monsterName: String) { self.town = town name = monsterName } func terrorizeTown() { if town != nil { print("\(name) is terrorizing a town!") }else { print("\(name) hasn't found a town to terrorize yet..") } } }

Here is the Town struct:

import Foundation struct Town { var mayor: Mayor? let region: String var population: Int { didSet(oldPopulation) { if population < oldPopulation { print("The population has changed to \(population) from \ (oldPopulation).") mayor?.mayorResponse() } } } var numberOfStoplights: Int init(region: String, population: Int, stoplights: Int) { self.region = region self.population = population numberOfStoplights = stoplights } init(population: Int, stoplights: Int) { self.init(region: "N/A", population: population, stoplights: stoplights) } enum Size { case Small case Medium case Large } var townSize: Size { get { switch self.population { case 0...10000: return Size.Small case 10001...100000: return Size.Medium default: return Size.Large } } } func printTownDescription () { print("Population: \(population); number of stoplights: \ (numberOfStoplights); region: \(region)") } mutating func changePopulation(_ amount: Int) { population += amount } }

Why am I receiving this error message?

show the Town class.

nayem
– nayem

2017-06-22 02:27:24 +00:00
Commented Jun 22, 2017 at 2:27 — nayem
– nayem, Commented Jun 22, 2017 at 2:27
I added the Town struct.

user2959094
– user2959094

2017-06-22 06:45:01 +00:00
Commented Jun 22, 2017 at 6:45 — user2959094
– user2959094, Commented Jun 22, 2017 at 6:45

vadian · Accepted Answer · 2017-06-22 07:46:32Z

2

The error is pretty clear

Cannot convert value of type 'Town?.Type' (aka 'Optional.Type') to expected argument type 'Town?

means that you are passing a type rather than the instance of the type.

Instead of Town? pass town:

vampirePopulation.append(Vampire(town: town, monsterName: name))

edited Jun 22, 2017 at 7:46

answered Jun 22, 2017 at 7:02

vadian

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3 Comments

user2959094 Over a year ago

But then I get the same error but for monsterName: String. When I change monsterName: String to monsterName: name all the errors go away. I understand that you're telling me that I need to pass an instance of the type for the arguments, but could you explain WHY? I want to understand why I'm doing this. Thanks!

vadian Over a year ago

An initializer like Vampire(town: Town?, monsterName: String) declares the parameter label and the associated type. When you call it you have to pass an instance of this type respectively. Look at the initializer init(population: Int, stoplights: Int). It calls the region initializer and passes the parameters accordingly.

user2959094 Over a year ago

Thank you so much!

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