Task model

Design the Task data class and list structure.

Task model: data class Task

In this project you will build a to-do app step by step. The first step is to define data class Task that represents a task.

data class Task(val title: String, val done: Boolean = false) {
    fun format() = if (done) "[x] $title" else "[ ] $title"
}

Each task has a title (title) and a completion state (done). done starts as false. The format function yields [x] title when done, otherwise [ ] title.

data class and equals

The biggest advantage of a data class is that equals is content-based: two Tasks are equal if their fields match. This makes search and indexOf on a list content-based.

val a = Task("Shopping")
val b = Task("Shopping")
a == b   // true
a.equals(b)  // true

This makes it easy for completeTask later to find a task with indexOfFirst.

Exercise Define the Task data class and print it

Define a data class Task(val title: String, val done: Boolean = false) with a body containing fun format() = if (done) "[x] $title" else "[ ] $title". In main create val t = Task("Shopping") and print it with println(t.format()).

Show example solution

fun main() {
    val t = Task("Shopping")
    println(t.format())
}

data class Task(val title: String, val done: Boolean = false) {
    fun format() = if (done) "[x] $title" else "[ ] $title"
}

Test yourself

What does a data class generate automatically?
- Only equals is generated
- Only toString is generated
- toString, equals, hashCode, copy are generated
- Nothing is generated
Show answer

toString, equals, hashCode, copy are generated — A data class auto-generates toString, equals, hashCode and copy.

Fill in the blank: data class

____ class Task(val title: String, val done: Boolean = false)

Show answer

data class Task(val title: String, val done: Boolean = false)

Match class part to role

data class Task

Data class
val title

Immutable title
val done

Immutable completion
format()

Readable output

Next lesson: Adding tasks

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies