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Returning Books

Part of the Object Oriented Programming section of Coddy's Kotlin journey. Lesson 52 of 57.

Challenge

Easy

Add the RETURN command. Your code from the previous step is already in Library.kt; keep every command working exactly as before.

RETURN <name> <id>: reply no member bo or no book 9 as for borrowing; if the member does not hold that book reply ada does not have Dune; otherwise remove the loan from the member, make the book available and reply ada returned Dune.

The supplied code passes every input line to library.handle(line) and prints each returned reply on its own line. Member names are single lower-case words, book ids are whole numbers, and the input holds only the commands described so far. Any other command replies unknown command.

Your code goes in Book.kt, Member.kt and Library.kt. Main.kt holds the supplied input/output code and cannot be edited.

Try it yourself

fun main() {
    // Supplied input/output code: keep it as it is
    val input = generateSequence(::readLine).toList()
    val library = Library()
    for (line in input) {
        for (reply in library.handle(line)) println(reply)
    }
}

All lessons in Object Oriented Programming

1Classes and Objects

Working With Files Defining Classes Primary Constructors init Blocks and Validation Secondary Constructors Recap - Library Card

4Inheritance

Open Classes and Subclasses Overriding Members super and Constructors Abstract Classes Recap - Staff Directory

7Special Classes

Data Classes Enum Classes Sealed Hierarchies equals, hashCode, toString Recap - Order Tracker

10Design Patterns Part 2

Delegation With by Decorator Pattern Builder Pattern State Pattern

2Properties and Encapsulation

Custom Accessors Visibility Modifiers Private Setters lazy and lateinit Recap - Bank Account

5Interfaces

Declaring Interfaces Default Methods Multiple Interfaces Interfaces as Types Recap - Payment Methods

8Generics

Generic Functions Generic Classes Type Constraints Variance With in and out Recap - Priority Queue

11Project: Library Management

Books and Members Borrowing Books

Project lesson

Returning Books Project lesson

Project lesson

Searching the Catalogue

Project lesson

Project lesson

3Objects and Companions

Object Declarations Companion Objects Constants With const Object Expressions Recap - Ticket Office

6Polymorphism

Dynamic Dispatch Type Checks and Smart Casts when With Types Extension Functions Recap - Zoo Keeper

9Design Patterns Part 1

Singleton Pattern Factory Pattern Observer Pattern Strategy Pattern

12Final Challenges

Parking Garage Event Scheduler Bank Ledger

Practice on your own: Kotlin playground