I'm a beginner in Swift and static programming. Going through Big Nerd Ranch Swift book. What I don't understand is why myTown population is changing, but not fredTheZombie.town? The exercise calls for the town population to never go below zero. This could happen when the population is less than 10. How do I change the fredTheZombie.town population variable?
struct Town {
var population = 5422
var numberOfStoplights = 4
func printTownDescription() {
print("Population: \(myTown.population), number of stoplights: \(myTown.numberOfStoplights)")
}
mutating func changePopulation(amount: Int) {
population += amount
}
}
class Monster {
var town: Town?
var name = "Monster"
func terrorizeTown() {
if town != nil {
print("\(name) is terrorizing a town!")
} else {
print("\(name) hasn't found a town to terrorize yet...")
}
}
}
class Zombie: Monster {
var walksWithLimp = true
final override func terrorizeTown() {
guard town?.population > 0 else {
return
}
if town?.population > 10 {
super.town!.changePopulation(-10)
} else {
super.town!.population = 0
}
super.terrorizeTown()
}
func changeName(name: String, walksWithLimp: Bool) {
self.name = name
self.walksWithLimp = walksWithLimp
}
}
var myTown = Town()
myTown.changePopulation(500)
let fredTheZombie = Zombie()
fredTheZombie.town = myTown
fredTheZombie.terrorizeTown()
fredTheZombie.town?.printTownDescription()
fredTheZombie.changeName("Fred the Zombie", walksWithLimp: false)
myTown.changePopulation(-5915)
print(myTown.population)
print(fredTheZombie.town!.population)
fredTheZombie.terrorizeTown()
fredTheZombie.terrorizeTown()
fredTheZombie.town?.printTownDescription()
Output:
Monster is terrorizing a town!
Population: 5922, number of stoplights: 4
7
5912
Fred the Zombie is terrorizing a town!
Fred the Zombie is terrorizing a town!
Population: 7, number of stoplights: 4
Program ended with exit code: 0
Town is a struct, a value type. When assigning a value type to a different variable (e.g. fredTheZombie.town = myTown), that value type is copied (meaning that a new Town is created with the same values as the original Town).
myTown and fredTheZombie.town are not the same town any more. If you want them to be the same instance, make them a class (a reference type).
See more info on Apple Swift Blog and in Swift Language Guide.
The biggest problem we have are optional structs. The result of unwrapping an optional struct (using town!) is again a copy, a new town. To work around that, you have to:
var myTown = super.town!
myTown.changePopulation(-10)
super.town = myTown // assign back
Whole example:
struct Town {
var population = 5422
var numberOfStoplights = 4
func printTownDescription() {
// note you have to print "self" here, not "myTown"
print("Population: \(self.population), number of stoplights: \(self.numberOfStoplights)")
}
mutating func changePopulation(amount: Int) {
population += amount
}
}
class Monster {
var town: Town?
var name = "Monster"
func terrorizeTown() {
if town != nil {
print("\(name) is terrorizing a town!")
} else {
print("\(name) hasn't found a town to terrorize yet...")
}
}
}
class Zombie: Monster {
var walksWithLimp = true
final override func terrorizeTown() {
guard super.town?.population > 0 else {
return
}
var town = super.town!
if town.population > 10 {
town.changePopulation(-10)
} else {
town.population = 0
}
super.town = town
super.terrorizeTown()
}
func changeName(name: String, walksWithLimp: Bool) {
self.name = name
self.walksWithLimp = walksWithLimp
}
}
In your case there is no need for town to be actually optional. You could just pass it to Monster in a constructor.
Related
I am very new to Swift so I apologize upfront if this is a "dumb" question. I am just working on a playgrounds script for generating random items, in this case, weapons. When I run my code I get this error: error: Execution was interrupted, reason: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0). What I was trying to do is hold an instance of a structure(which is handle) in my class normalBladeType in variable weaponHandle. I've tried researching about this topic but I've yet to find an answer. Any suggestions would be great. For all I know I may be going about this all wrong.
Thanks,
my code:
//: Playground - noun: a place where people can play
import Cocoa
let handleWoods = ["White Ash", "Oak", "White Oak", "Elm", "Maple","Walnut", "Cherry", "Rosewood", "Ash", "Hickory", "Birch", "Hemlock", "Cedar", "Pine"]
let handleGrips = ["Leather", "Buckskin", "Sharkskin", "Goat Skin", "Deerskin", "Elk Skin", "Rayskin", "Snakeskin", "Silk Cord", "Cotton Cord"]
let gripQualities = ["Simple", "Interwoven", "Ornate", "Smooth", "Thin", "Thick", "Ruff", "Worn"]
func returnRandomItem( _ list: [Any])-> Any {
return list[Int(UInt32(list.count))]
}
struct handle {
var name: String
var value, grip: Int
var weight: Double
var withGrip: Bool
init(withGrip: Bool) {
self.weight = 0.25
self.withGrip = withGrip
let handleNameWithWood = "\(returnRandomItem(handleWoods)) Handle"
if self.withGrip {
let randGrip = "\(returnRandomItem(gripQualities)) \(returnRandomItem(handleGrips)) Grip)"
self.name = "\(randGrip) (\(handleNameWithWood))"
self.grip = 75
self.value = 2
} else {
self.name = handleNameWithWood
self.grip = 50
self.value = 1
}
}
func description() {
print("Handle Description \(self.name)")
}
}
class weapon {
var TypeOfWeapon: String
var weaponHandle: handle
init(weaponType: String, doesHaveGrip: Bool) {
self.TypeOfWeapon = weaponType
self.weaponHandle = handle(withGrip: doesHaveGrip)
}
}
class normalBladeType: weapon {
init() {
super.init(weaponType: "normalBladeType", doesHaveGrip: false)
}
func description() {
print("TypeOfWeapon: \(self.TypeOfWeapon)")
print("TypeDescription: normal hilt (guard - handle - pommel) + straight blade")
}
}
var foo = normalBladeType()
foo.description()
Your returnRandomItem function is wrong. You should change it to
func returnRandomItem( _ list: [Any])-> Any {
let index: UInt32 = arc4random_uniform(UInt32(list.count))
return list[Int(index)]
}
It is working fine for me with this code.
I'm learning swift from a book and typed an example of structs and classes. However the example does not work like it should because the program won't decrease the population whenever a zombie is called. I know this is a stupid question but I just can't understand why. Can somebody explain what's wrong? So here's the code:
main.swift
import Foundation
var myTown = Town()
myTown.changePopulation(by:500)
let fredTheZombie = Zombie()
fredTheZombie.town = myTown
fredTheZombie.terrorizeTown()
fredTheZombie.town?.printDescription()
myTown.printDescription()
Town.swift
import Foundation
struct Town {
var population = 5422
var numberOfStopLights = 4
func printDescription() {
print("Population: \(myTown.population), number of stoplights: \ . (myTown.numberOfStopLights).")
}
mutating func changePopulation(by amount: Int){
population += amount
}
}
Monster.swift
import Foundation
class Monster{
var town: Town?
var name = "Monster"
func terrorizeTown(){
if town != nil{
print("\(name) is terrorazing a town!")
}
else{
print("\(name) hasn't found a town to terrorize yet...")
}
}
}
Zombie.swift
import Foundation
class Zombie: Monster {
override func terrorizeTown() {
town?.changePopulation(by: -10)
super.terrorizeTown()
}
}
If you change Town from a struct to a class it will work.
A struct is copied each time you assign it, so when you put zombie.town = myTown it is not the same town, the zombie has a copy of the town and the original town is not changed when the zombie's town is updated. A class will work the way you expect it to.
Since Town is a struct, it will be copied when you assign it to your zombie. Therefore, fredTheZombie.terrorizeTown() terrorizes a copy of myTown - so myTown keeps it's value.
What you want is a class, which will be transferred by reference when you assign it to your monster -- so you only have one Town:
class Town {
var population = 5422
var numberOfStopLights = 4
func printDescription() {
print("Population: \(myTown.population), number of stoplights: \ . (myTown.numberOfStopLights).")
}
func changePopulation(by amount: Int){
population += amount
}
}
I'd like to learn how to set a unique gifted dance property during initialization using a breakdances enum that uses strings. I figured it would work but when I tried different variations of setting the property in init, I would get compile errors such as "assigning a property to itself" and many others. I've run out of ideas but I know its possible because some Cocoa classes do this during initialization such as UITableView when selecting preferred style.
import Foundation
enum Breakdances: String {
case HoppityHop = "Hop Hop Hop and two step is what I do usually"
case Greyjoy = "I made up this dance, pretty cool huh?"
case ButtSwirl = "Let's do the butt swril"
case PsychMovementWithHands = "Psych, Psych, Psych! Psych"
case TheDab = "Dabbbbb!"
case TheBump = "I'm doing the rump bump dance"
}
class Monkeys: Animals, canPlayAroundProtocol, randomJungleActivity {
static var monkeysPopulation: Int = 0
var uniqueGiftedDance: Breakdances
override init(name:String){
super.init(name: name)
self.uniqueGiftedDance = uniqueGiftedDance
Monkeys.monkeysPopulation += 1
}
override func makeSound() -> String {
energyLevel -= 4
return "Ah ah ah"
}
override func eatFood(){
energyLevel += 2
}
override func sleep(){
}
func play(){
let reducedEnergy = energyLevel - 8
if reducedEnergy < 0 {
print("\(name) is too tired, I don't have enough energy")
}else {
print("Oooo Oooo Oooo")
print("\(name)'s energy level is now \(reducedEnergy)")
}
}
func startUniqueJungleAct(){
print(uniqueGiftedDance)
print("Swinging from a tree and throwing banannas")
}
deinit {
Monkeys.monkeysPopulation -= 1
}
}
Here is my parent class:
import Foundation
protocol canPlayAroundProtocol {
func play()
}
protocol randomJungleActivity {
func startUniqueJungleAct()
}
class Animals {
static var animalPopulation: Int = 0
var name: String!
var energyLevel: Int = 100
init(name: String) {
self.name = name
Animals.animalPopulation += 1
print("Another animal has given birth, animal population is now \(Animals.animalPopulation)")
}
func makeSound() -> String{
energyLevel -= 3
return "null"
}
func eatFood() {
energyLevel += 5
}
func sleep(){
energyLevel += 10
}
static func junglePerformSoundOff(){
}
func bathroomSound(){
}
deinit {
Animals.animalPopulation -= 1
}
}
You just need to add a new parameter to your initializer.
init(name: String, uniqueGiftedDance: Breakdances) {
super.init(name: name)
self.uniqueGiftedDance = uniqueGiftedDance
Monkeys.monkeysPopulation += 1
}
I have a struct Town
with a population of 11
struct Town {
var population: Int = 11 {
didSet(oldPopulation){
print("The population has changed to \(population) from \(oldPopulation)")
}
}
}
and I have a mutating function
mutating func changePopulation(amount: Int) {
population += amount
}
I created a zombie class that calls a function that decreases population by 10
final override func terrorizeTown() {
guard var town = town else {
return
}
town.population <= 0 ? print("no people to terrorize") : town.changePopulation(amount: -10)
super.terrorizeTown()
}
when I run this i the main.swift file
var myTown = Town()
var fredTheZombie = Zombie()
fredTheZombie.name = "Fred"
fredTheZombie.town = myTown
//myTown.changePopulation(amount: 0)
print(myTown.population)
fredTheZombie.terrorizeTown()
print(myTown.population)
What I don't understand is the results..
11
The population has changed to 1 from 11
Fred is terrorizing a town!
11
Why is it that when I print (myTown.population) again do i receive a value of 11, when I have called a mutating function on the property. I don't understand.. should the result not be 1, why do i get 11?
It is because the line guard var town = town makes a copy of your Town object. Hence, it is the copy that is mutated.
Hi I am doing some Swift coding and I cant figure out how to get rid of this error:
Missing argument for parameter 'makePetMakeNoise' in call.
Could you help me fix this error?
import Foundation
import UIKit
class Human {
static var numCreated:Int = 4
var name:String = ""
var pet:Pet
init(name:String,pet:Pet){
self.name = name
self.pet = pet
Human.numCreated++
}
func makePetMakeNoise(){
var randomNumber = arc4random_uniform(9)
self.pet.makeNoise(randomNumber) //Missing argument for parameter 'makePetMakeNoise' in call
}
func feedPet(){
self.pet.eat
}
static func populationCount(){
println("Total population count is \(Human.numCreated)")
}
}
class Pet {
var name:String = ""
var noise:String = ""
var canMakeNoise:Bool = true
init(name:String,noise:String,canMakeNoise:Bool){
self.name = name
self.noise = noise
self.canMakeNoise = canMakeNoise
}
func makeNoise(canMakeNoise: Int, makePetMakeNoise: Int){
if self.canMakeNoise {
for _ in 1...5{
println("\(self.name) \(self.noise)")
}
}else {
println("\(self.name) *remains silent*")
}
}
func eat(){
println("\(name) is eating")
}
class Dog:Pet{
}
class Cat:Pet{
override func eat {
super.eat()
println("I'm still hungry, meow")
}
}
}
//Pets
var Tobie = Pet(name: "Tobie", noise: "Bark", canMakeNoise: true)
var Bud = Pet(name: "Bud", noise: "Bark", canMakeNoise: false)
var Ginger = Pet(name: "Ginger", noise: "bark", canMakeNoise: false)
var Curry = Pet(name: "Curry", noise: "Bark", canMakeNoise: true)
//Humans
var Sam = Human(name: "Sam", pet: Tobie)
var Mark = Human(name: "Mark", pet: Bud)
var Spencer = Human(name: "Spencer", pet: Ginger)
var Jessie = Human(name: "Jessie", pet: Curry)
let Humans = [Sam, Mark, Spencer, Jessie]
for Human in Humans {
println("\(Humans) \(feedPet) \(makePetMakeNoise)") //Use of unresolved identifier 'feedPet and makePetMakeNoise'\\
}
`
Your makeNoise method defined for Pet takes two parameters. Problem is that when you call it in the line that gives you the error, you pass it just one parameter.
Possible solution is:
Change the Pet's method as follow:
func makeNoise(makePetMakeNoise: Int){
if self.canMakeNoise {
for _ in 1...5{
println("\(self.name) \(self.noise)")
}
}else {
println("\(self.name) *remains silent*")
}
}
Update the code that gives you the error in Human like this:
func makePetMakeNoise(){
var randomNumber = Int(arc4random_uniform(9))
self.pet.makeNoise(randomNumber)
}
Notice I convert random to Int since this is the expected parameter type.
Please consider I'm just guessing a possible modification since I don't know what your classes are intended for ... maybe just a playground.
Other solution is effectively passing two parameters when you call the pet's method from human.
Hope this helps
Your function func makeNoise(canMakeNoise: Int, makePetMakeNoise: Int) expects two arguments, but your are only passing the one randonNumber in your call self.pet.makeNoise(randomNumber). It should look something like this: self.pet.makeNoise(randomNumber, someOtherNumber)