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Exercise: GUI View Hierarchy Simulation

Implement the following classes and methods, that will represent a view hierarchy in a GUI system:
  1. Create an open class View with primary constructor properties: read-only id of type String and read-write isVisible of type Boolean.
  2. Implement methods show and hide in the View class, that will change the isVisible property to true and false respectively.
  3. Create two subclasses of View: TextView and Toggle.
  4. TextView should have a constructor with parameter id and property text, that will represent the text displayed in the view. It should set superclass isVisible property to true.
  5. Toggle should have a constructor with parameter id. It should set superclass isVisible property to true.
  6. Toggle should have an additional property isOn, that will represent the state of the toggle. It should be initially set to false.
  7. Toggle should have a method click, that will change the isOn property to the opposite state.
Example usage:
val view = View(
    id = "v1",
    isVisible = false,
)
println(view.id) // v1
println(view.isVisible) // false

val textView = TextView(
    id = "tv1",
    text = "Hello, World!",
)
println(textView.id) // tv1
println(textView.text) // Hello, World!
println(textView.isVisible) // true

textView.text = "Welcome to Kotlin!"
println(textView.text) // Welcome to Kotlin!

textView.hide()
println(textView.isVisible) // false

val toggle = Toggle(
    id = "toggle1",
)
println(toggle.id) // toggle1

println(toggle.isOn) // false
toggle.click()
println(toggle.isOn) // true

println(toggle.isVisible) // true
toggle.hide()
println(toggle.isVisible) // false
toggle.show()
println(toggle.isVisible) // true
This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in essentials/classes/Gui.kt. You can find there example usage and unit tests.
Once you are done with the exercise, you can check your solution here.

Playground

import junit.framework.TestCase.assertFalse
import junit.framework.TestCase.assertTrue
import org.junit.Test
import kotlin.test.assertEquals

// TODO

fun main() {
    val view = View(
        id = "v1",
        isVisible = false,
    )
    println(view.id) // v1
    println(view.isVisible) // false
    
    val textView = TextView(
        id = "tv1",
        text = "Hello, World!",
    )
    println(textView.id) // tv1
    println(textView.text) // Hello, World!
    println(textView.isVisible) // true
    
    textView.text = "Welcome to Kotlin!"
    println(textView.text) // Welcome to Kotlin!
    
    textView.hide()
    println(textView.isVisible) // false
    
    val toggle = Toggle(
        id = "toggle1",
    )
    println(toggle.id) // toggle1
    
    println(toggle.isOn) // false
    toggle.click()
    println(toggle.isOn) // true
    
    println(toggle.isVisible) // true
    toggle.hide()
    println(toggle.isVisible) // false
    toggle.show()
    println(toggle.isVisible) // true
}

class GuiTests {

    @Test
    fun `view show should set isVisible to true`() {
        val view = View("view1", false)
        view.show()
        assertTrue(view.isVisible)
    }

    @Test
    fun `view hide should set isVisible to false`() {
        val view = View("view2", true)
        view.hide()
        assertFalse(view.isVisible)
    }

    @Test
    fun `toggle click should toggle isOn state`() {
        val toggle = Toggle("toggle1")
        toggle.click()
        assertTrue(toggle.isOn)
        toggle.click()
        assertFalse(toggle.isOn)
    }

    @Test
    fun `text view setText should update text property`() {
        val textView = TextView("textView1", "Hello")
        textView.text = "World"
        assertEquals("World", textView.text)
    }

    @Test
    fun `toggle should inherit properties from view`() {
        val toggle = Toggle("toggle2")
        assertTrue(toggle.isVisible)
        toggle.hide()
        assertFalse(toggle.isVisible)
    }

    @Test
    fun `text view should inherit properties from view`() {
        val textView = TextView("textView2", "Hello")
        assertTrue(textView.isVisible)
    }

    @Test
    fun `toggle should start with isOn set to false`() {
        val toggle = Toggle("toggle3")
        assertFalse(toggle.isOn)
    }

    @Test
    fun `toggle should toggle isOn state correctly`() {
        val toggle = Toggle("toggle4")
        toggle.click()
        assertTrue(toggle.isOn)
        toggle.click()
        assertFalse(toggle.isOn)
        toggle.click()
        assertTrue(toggle.isOn)
    }

    @Test
    fun `view show and hide interactions`() {
        val view = View("view3", false)
        view.show()
        assertTrue(view.isVisible)
        view.hide()
        assertFalse(view.isVisible)
    }

    @Test
    fun `text view setText and visibility interactions`() {
        val textView = TextView("textView3", "Hello")
        textView.text = "World"
        assertEquals("World", textView.text)
        textView.hide()
        assertFalse(textView.isVisible)
    }
}