Type casting with as, as?, as! in Swift - Mini Project: Build & Apply

Type Casting with as, as?, as! in Swift

📖 Scenario: Imagine you are building a simple app that manages a list of different types of vehicles. Each vehicle can be a Car or a Bicycle. You want to check the type of each vehicle and print specific details.

🎯 Goal: You will create a list of vehicles, add a configuration variable to control safe casting, use type casting with as, as?, and as! to identify vehicle types, and finally print the details.

📋 What You'll Learn

Create a list called vehicles containing exactly two objects: a Car and a Bicycle

Create a Boolean variable called useSafeCasting set to true

Use a for loop with variables vehicle to iterate over vehicles and use as? for safe casting when useSafeCasting is true, otherwise use as! for forced casting

Print the type and details of each vehicle using print()

💡 Why This Matters

🌍 Real World

Type casting is useful when you have a list of mixed objects and need to work with their specific types safely or forcefully.

💼 Career

Understanding type casting helps in writing safer and more flexible Swift code, especially when working with collections of different object types in apps.

1

Create the vehicle classes and the vehicles list

Create a class called Car with a property model set to "Sedan" and a class called Bicycle with a property type set to "Mountain". Then create a list called vehicles containing one Car() and one Bicycle().

Swift

# Define classes Car and Bicycle
# Create list vehicles with Car() and Bicycle()
# Your code here

Need a hint?

Define two simple classes with one property each. Then create a list called vehicles that holds one instance of each class.

2

Add a configuration variable for safe casting

Create a Boolean variable called useSafeCasting and set it to true.

Swift

class Car {
    var model = "Sedan"
}

class Bicycle {
    var type = "Mountain"
}

let vehicles: [Any] = [Car(), Bicycle()]

// Create useSafeCasting variable
# Your code here

Need a hint?

Just create a Boolean variable named useSafeCasting and set it to true.

3

Use type casting with as?, as! inside a loop

Use a for loop with variable vehicle to iterate over vehicles. Inside the loop, if useSafeCasting is true, use as? to safely cast vehicle to Car or Bicycle. If useSafeCasting is false, use forced casting as! instead.

Swift

class Car {
    var model = "Sedan"
}

class Bicycle {
    var type = "Mountain"
}

let vehicles: [Any] = [Car(), Bicycle()]

let useSafeCasting = true

// Loop over vehicles and cast using as? or as!
# Your code here

Need a hint?

Use a for loop to check each vehicle. Use as? for safe casting when useSafeCasting is true, otherwise use as! for forced casting. Use if let to unwrap safely.

4

Print the vehicle details

Print the type and details of each vehicle inside the loop using print(). For example, print "Safe cast: Car model is Sedan" or "Safe cast: Bicycle type is Mountain" depending on the cast.

Swift

class Car {
    var model = "Sedan"
}

class Bicycle {
    var type = "Mountain"
}

let vehicles: [Any] = [Car(), Bicycle()]

let useSafeCasting = true

for vehicle in vehicles {
    if useSafeCasting {
        if let car = vehicle as? Car {
            // Print car details
        } else if let bike = vehicle as? Bicycle {
            // Print bicycle details
        }
    } else {
        if let car = vehicle as! Car? {
            // Print car details
        } else if let bike = vehicle as! Bicycle? {
            // Print bicycle details
        }
    }
}
# Your code here

Need a hint?

Use print() inside the loop to show the vehicle type and its property value after casting.