30 Days of SwiftUI - Day 6: Mastering Structs and Property Management in Swift

 

🏗️ Building Blocks of Swift: Creating Your Own Structs

Structs are a powerful way to build custom data types in Swift. They group related data and functionality in a neat package.

Example:

struct Car {
    var brand: String
    var year: Int
}

let myCar = Car(brand: "Tesla", year: 2024)
print(myCar.brand) // Output: Tesla

---

🔎 Struct vs Tuple: What's the Difference?

Feature	Struct	Tuple
Named Properties	Yes	Optional
Methods & Computed Properties	Yes	No
Flexibility	Highly Flexible	Lightweight & Fixed

Use structs for complex data models and tuples for quick, lightweight data combinations.

---

🛠️ Methods vs Functions: Spot the Difference

• Functions exist independently, outside of types.

• Methods are functions defined inside types (e.g., structs, classes).

Example:

struct Calculator {
    func add(a: Int, b: Int) -> Int {
        return a + b
    }
}

let calc = Calculator()
print(calc.add(a: 3, b: 5)) // Output: 8

---

🔄 Why Use mutating Methods?

If a method modifies any properties of a struct, it must be marked as mutating.

Example:

struct Counter {
    var value = 0

    mutating func increment() {
        value += 1
    }
}

var counter = Counter()
counter.increment()
print(counter.value) // Output: 1

---

🧮 Dynamic Data: Computed Properties in Action

Computed properties are properties that calculate their values dynamically.

Example:

struct Circle {
    var radius: Double

    var area: Double {
        3.14 * radius * radius
    }
}

let circle = Circle(radius: 5)
print(circle.area) // Output: 78.5

---

🤔 Stored vs Computed Properties: Which to Use?

• Use stored properties to store fixed values.

• Use computed properties when the value is derived from other properties.

---

📡 Reacting to Change: Property Observers

Swift's property observers let you monitor property changes using willSet and didSet.

Example:

struct ProgressTracker {
    var progress = 0 {
        willSet { print("Progress about to change to \(newValue)") }
        didSet { print("Progress changed from \(oldValue) to \(progress)") }
    }
}

var tracker = ProgressTracker()
tracker.progress = 50

---

⚙️ willSet vs didSet: When to Use Which?

• Use **willSet** when you need to act before the value changes.

• Use **didSet** when you need to react after the value changes.

---

🚀 Custom Initializers: Crafting Personalized Structs

Swift allows you to create custom initializers to set up complex values.

Example:

struct Book {
    var title: String
    var author: String

    init(title: String, author: String) {
        self.title = title
        self.author = author
    }
}

let book = Book(title: "Swift Mastery", author: "Gati Shah")

---

🔐 Memberwise Initializers in Swift

Swift automatically generates an initializer for structs if no custom one exists.

Example:

struct Laptop {
    var brand: String
    var model: String
}

let myLaptop = Laptop(brand: "Apple", model: "MacBook Pro")

---

🙋‍♀️ Using self in Methods: Why and When?

Use self to distinguish between parameter names and property names or to clarify code in closures.

Example:

struct Person {
    var name: String

    func introduce() {
        print("Hello, I'm \(self.name)")
    }
}

---

🚨 Locking It Down: Mastering Access Control

Access control defines who can use your code and how they interact with it.

Modifier	Scope
private	Accessible only inside the same type
fileprivate	Accessible within the same file
internal	Accessible within the same module (default)
public	Accessible from any module
open	Same as public, but allows subclassing outside the module

---

🔒 Protecting Data: Limiting Access with Access Control

Access control is key to keeping sensitive data secure and controlling your API's usage.

Example:

struct BankAccount {
    private var balance: Double = 0

    mutating func deposit(amount: Double) {
        balance += amount
        print("New balance: \(balance)")
    }
}

---

🌍 Why Use Access Control?

• Prevent accidental property modifications.

• Improve security by limiting data exposure.

• Ensure better code structure and clarity.

---

🧱 Static Properties & Methods: The Power of One

Static properties and methods belong to the type itself rather than an instance.

Example:

struct Configuration {
    static let appName = "SwiftMaster"

    static func printAppName() {
        print("App Name: \(appName)")
    }
}

Configuration.printAppName() // Output: App Name: SwiftMaster

---

📋 Why Use Static Properties & Methods?

• Ideal for constants and shared functionality.

• Efficient when you don't need individual instances.

---

✅ Checkpoint Challenge: Test Your Skills!

Question: Create a struct called Rectangle with width and height properties, a method that calculates its area, and a property observer that prints when the width changes.

Answer:

struct Rectangle {
    var width: Double {
        didSet { print("Width updated to \(width)") }
    }
    var height: Double

    func area() -> Double {
        return width * height
    }
}

var rect = Rectangle(width: 5, height: 10)
print(rect.area())
rect.width = 8 // Output: Width updated to 8