Lynda Course - Swift 5 Essential Thinking (Part 6)

Here we go! A quick session now. Not sure how long I've got but gonna do a bit. A couple more chapters of this course, then will review what else from Lynda is worth looking at. At some point I need to decide if the subscription is worth it. 

 Start Time - 12:57

6. Classes, Structs and Beyond

So I looked at the initial couple of videos last time about value vs reference types. Now the focus is specifically on classes.

Classes

All this is fine - just a recap -

class Adventurer {
    
    var name: String
    var maxHealth: Int
    
    
    var specialMove: String?
    
    init(name: String, maxHP: Int) {
        self.name = name
        self.maxHealth = maxHP
    }
    
    convenience init(name: String) {
        self.init(name: name, maxHP: 100)
    }
}

var player1 = Adventurer(name: "Steve", maxHP: 75)

var player2 = Adventurer(name: "Dwayne")

var player3 = player1

So a key point now is that any change to player3 will also happen to player1 (Reference type remember!).

player3.maxHealth = 45

Access Modifiers and Properties

Four levels of access - public, internal, file private and private. 

Get and set - within computed properties

A few more bits added to the code - 

  var healthLost: Int {
        return maxHealth - 50
    }
    
    fileprivate var health: Int

    var Health: Int {
        get { return health }
        set { if newValue <= 100 {
            health = newValue
            }
        }
    }
    
    init(name: String, maxHP: Int) {
        self.name = name
        self.maxHealth = maxHP
        self.health = maxHP
    }
    
    convenience init(name: String) {
        self.init(name: name, maxHP: 100)
    }

So for the above, we have a filerprivate var - that cannot be accessed outside of the class. But it did need intialising. 

For the computed properties, one had get/set (Health). The other (healthLost) was read only. 

Now a word about type variables - use of static and class keywords. 

static var maxActivePlayers = 10
    
    class var credo: String {
        return "Defend all my friend!"
    }

A couple of notes here - the static var cannot be altered in a subclass. The class one can. You can not access these properties on an object/instance of a class, only the class itself. 

Useful for storing variables that are global to a class or struct. 

Subclassing In Swift

SO here is the syntax for the init part - 

class Ranger: Adventurer {
    
    var classAdvantage: String
    
    init(name: String, advantage: String) {
        self.classAdvantage = advantage
        super.init(name: name, maxHP: 150)
    }
}

I'm going to stop there - saved! Will add to and continue this entry a bit more later so classes are done. 

Stopped at 13:23 (26 minutes so far)

 OK so I wasn't able to add again that day, I'm doing so the next day - the rest of this chapter before bed!

Start Time - 21:01
struct Level {
    let levelID: Int
    var levelObjective: [String]
    
    var levelDescription: String {
        return "Level ID: \(self.levelID)"
    }
    
    init(id: Int, objectives: [String]) {
        self.levelID = id
        self.levelObjective = objectives
    }
    
    func queryObjective() {
        for objective in levelObjective {
            print("\(objective)")
        }
    }
    
    mutating func completeObjective(index: Int) {
        levelObjective.remove(at: index)
    }

}


A key point here is that the struct is a value type. So a copy is made for each instance.

Lots of stuff here. Including optional chaining....

struct Item {
    var description: String
    var previousOwner: Owner?
}

struct Owner {
    var name: String
    
    func returnOwnerInfo() -> String {
        return "The owner is: \(name)"
    }
}

var questDirectory = [
    "Fetch Gemstones": [
        "Objective": "Retrieve 5 gemstones",
        "Secret": "Complete in under 5 minutes"
    ],
    "Defeat Big Boss": [
        "Objective": "Beat the ultimate boss",
        "Secret": "Win with 50% health left"
    ]
]

// Creating the chain

var rareDagger = Item(description: "A rather strange, jagged object", previousOwner: nil)

if let owner = rareDagger.previousOwner?.name {
    print("This item used to be owned by \(owner)")
} else {
    print("OK so the history is unknown")
}

let daggerOwner = Owner(name: "Roland")

rareDagger.previousOwner = daggerOwner

rareDagger.previousOwner?.name = "The thief"

if let ownerInfo = rareDagger.previousOwner {
    print("Here is the info - the name is: \(ownerInfo.name)")
} else {
    print("No info")
}

if let gemstoneObjective = questDirectory["Fetch Gemstones"]?["Objective"] {
    print("This is the objective: \(gemstoneObjective)")
} else {
    print("Objective not found")

}


Right challenge time then bed! This is going to need classes, structs and optional chaining. Cool!


// 1

class Item {
    
    var name: String
    var price: Int
    
    var secret: BonusEffect?


// 2

init(name: String, price: Int) {
    self.name = name
    self.price = price
    }

}

// 3

struct BonusEffect {
    
    var bonus: Int
}

// 4

// 5

class Inventory {
    
    var storedItems: [Item]
    
// 6
    
    init(storedItems: [Item]) {
        self.storedItems = storedItems
    }
}



// 7
var sword = Item(name: "sword", price: 3)
var pistol = Item(name: "pistol", price: 8)

var extraAttack = BonusEffect(bonus: 2)

pistol.secret = extraAttack

// 8

var weaponsList = Inventory(storedItems: [sword, pistol])

if let weaponFact = pistol.secret {
    print("The special fact is \(weaponFact)")
} else {
    print("No special fact")
}


All seemed fine - just need to check if I had the right idea about 8!

OK, not quite for 8! Before I see the whole answer, let's just look again....

OK this is it!

var weaponsList = Inventory(storedItems: [sword, pistol])

if let weaponFact = weaponsList.storedItems[0].secret?.bonus {
    print("The special fact is \(weaponFact)")
} else {
    print("No special fact")
}

Needed a bit of help there - so something to practice is the optional chaining when there are custom types within an array. 

Finish Time - 21:54 (1 hour 19 minutes grand total)

So lots of useful stuff about classes and structs. Interestingly, not the usual basics but quite a bit involving optionals. When I've done this course (just one more chapter to go) there is plenty I would like to review and look over. 

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