Exercise Set 2: Struct, Protocol & Error Handling Practice

Let's think about this for a second

This exercise set is harder than Exercise Set 1, and it's meant to combine practice on the protocol, closure, enum with associated value, and error handling topics from the Intermediate/Advanced chapter. It's not new teaching content — it's a self-test where you apply the concepts by writing code yourself. The tasks are independent of the Task Manager project, designed so you can practice each concept in isolation. After solving each one, read any compile errors yourself and try to fix them.

Exercises

Task 1: Build a Shape protocol with a var area: Double { get } requirement and make Circle and Rectangle structs conform to it. Task 2: Build a [Circle] array and use closure-based sorted(by:) to sort it from smallest to largest area. Task 3: Build a NetworkResult enum with two associated values, success(data: String) and failure(reason: String), and handle both cases with a switch statement. Task 4: Write a validateAge(_ age: Int) throws -> Int function that throws a custom Error enum (InvalidAgeError) if age is below 0 or above 120, and handle it with do-catch.

• Do both Circle and Rectangle structs conform to the Shape protocol with correct area calculations?
• Does the closure-based sorted(by:) correctly sort the array by area order?
• Does the validateAge function correctly throw/catch a custom error for invalid cases?

Sample Code

// Task 1
protocol Shape {
    var area: Double { get }
}

struct Circle: Shape {
    let radius: Double
    var area: Double {
        // TODO: implement
        return 0
    }
}

struct Rectangle: Shape {
    let width: Double
    let height: Double
    var area: Double {
        // TODO: implement
        return 0
    }
}

// Task 2
let circles = [Circle(radius: 3), Circle(radius: 1), Circle(radius: 2)]
// TODO: sorted(by:) closure

// Task 3
enum NetworkResult {
    case success(data: String)
    case failure(reason: String)
}
// TODO: switch statement

// Task 4
enum InvalidAgeError: Error {
    case outOfRange
}
func validateAge(_ age: Int) throws -> Int {
    // TODO: implement
    return age
}

The Circle/Rectangle area calculations should be correct, the circles array should be sorted by radius order (1, 2, 3), and calling validateAge(150) should have the catch block correctly catch the InvalidAgeError.outOfRange error.