Understanding Optional Chaining in Swift Programming

Learn about optional chaining in Swift programming with examples involving students, dormitories, and room numbers. Explore how to handle optionals to avoid crashes and safely access nested properties.

• Optional Chaining
• Swift Programming
• Error Handling
• Nested Properties

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Uploaded on Oct 01, 2024 | 0 Views

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1. Ch14.

2. 14.1 (?) nil

3. // optional chaining class Student { var dorm: Dormitory? } class Dormitory { var numberOfRooms = 2 } let peter = Student() let rooms = peter.dorm?.numberOfRooms print("Dormitory has \(rooms) rooms")

4. Dormitory has nil rooms

5. 14.2 class Student { var dorm: Dormitory? } init(numberOfRooms: Int) { self.numberOfRooms = numberOfRooms } var location: Location? } class Dormitory { var numberOfRooms: Int class Location { var dormitoryName: String? var street: String? } func printNumberOfRooms() { print("The number of rooms is \(numberOfRooms)") }

6. 14.2.1

7. class Student { var dorm: Dormitory? } class Location { var dormitoryName: String? var street: String? } class Dormitory { var numberOfRooms: Int let peter = Student() if let roomNumber = peter.dorm?.numberOfRooms { print("Peter's dormitory has \(roomNumber) rooms") } else { print("Unabel to retrieve the number of rooms") } func printNumberOfRooms() { print("The number of rooms is \(numberOfRooms)") } init(numberOfRooms: Int) { self.numberOfRooms = numberOfRooms } var location: Location? }

8. Unabel to retrieve the number of rooms

9. 14.2.2 printNumberOfRooms

10. class Student { var dorm: Dormitory? } class Location { var dormitoryName: String? var street: String? } class Dormitory { var numberOfRooms: Int // call method let peter = Student() peter.dorm = Dormitory(numberOfRooms: 10) peter.dorm!.printNumberOfRooms() func printNumberOfRooms() { print("The number of rooms is \(numberOfRooms)") } init(numberOfRooms: Int) { self.numberOfRooms = numberOfRooms } var location: Location? }

11. The number of rooms is 10

12. 14.3 Location peterLocation Location peterLocation peter.dorm?.location

13. class Student { var dorm: Dormitory? } class Location { var dormitoryName: String? var street: String? } class Dormitory { var numberOfRooms: Int func printNumberOfRooms() { print("The number of rooms is \(numberOfRooms)") } init(numberOfRooms: Int) { self.numberOfRooms = numberOfRooms } var location: Location? } // multiple chain let peter = Student() peter.dorm = Dormitory(numberOfRooms: 10) let peterLocation = Location() peterLocation.dormitoryName = "BigHouse Building" peterLocation.street = "Hsingchang 777" peter.dorm?.location = peterLocation print(peter.dorm?.location?.dormitoryName) print(peter.dorm?.location?.street)

14. Optional(BigHouse Building) Optional(Hsingchang 777)