Enum with properties and methods in Kotlin - Step-by-Step Execution

Concept Flow - Enum with properties and methods

Define Enum Class

↓

Add Properties to Enum

↓

Add Methods to Enum

↓

Create Enum Instances

↓

Access Properties and Call Methods

↓

Use Enum in Code

This flow shows how to define an enum with properties and methods, create instances, and use them.

Execution Sample

Kotlin

enum class Color(val rgb: Int) {
    RED(0xFF0000) {
        override fun printInfo() = println("Red color with RGB: $rgb")
    },
    GREEN(0x00FF00) {
        override fun printInfo() = println("Green color with RGB: $rgb")
    },
    BLUE(0x0000FF) {
        override fun printInfo() = println("Blue color with RGB: $rgb")
    };

    abstract fun printInfo()
}

fun main() {
    val c = Color.RED
    c.printInfo()
}

Defines an enum Color with a property rgb and a method printInfo, then calls printInfo on RED.

Execution Table

Step	Action	Enum Instance	Property rgb	Method Called	Output
1	Enum Color is defined with RED, GREEN, BLUE	-	-	-	-
2	Main function starts	-	-	-	-
3	Assign c = Color.RED	RED	0xFF0000	-	-
4	Call c.printInfo()	RED	0xFF0000	printInfo()	Red color with RGB: 16711680
5	Program ends	-	-	-	-

💡 Program ends after calling printInfo on Color.RED

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
c	null	Color.RED (rgb=16711680)	Color.RED (rgb=16711680)	Color.RED (rgb=16711680)

Key Moments - 2 Insights

Why do we need to override printInfo() for each enum instance?

Each enum instance can have its own behavior. Overriding printInfo() lets each color print a custom message, as shown in execution_table step 4.

What does the property rgb represent and how is it used?

rgb holds the color code as an integer. It is passed when creating each enum instance and used inside printInfo() to show the color value (see step 4).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of c.rgb after step 3?

A 0xFF0000

B 0x0000FF

C 0x00FF00

D null

💡 Hint

Check the 'Property rgb' column at step 3 in the execution_table.

At which step is the method printInfo() called?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Method Called' column in the execution_table.

If we add a new enum instance YELLOW with rgb 0xFFFF00, what changes in the execution_table?

A A new row for YELLOW creation and method call would appear

B No changes, because YELLOW is not used in main

C The output at step 4 changes to Yellow color

D The program will not compile

💡 Hint

Check that main only uses Color.RED, so new enum instances don't affect existing steps.

Concept Snapshot

enum class Name(val property: Type) {
  INSTANCE1(value) {
    override fun method() { ... }
  },
  INSTANCE2(value) { ... };

  abstract fun method()
}

- Enums can have properties and methods.
- Each instance can override methods.
- Use enum instances like objects with behavior.

Full Transcript

This example shows how to define an enum class in Kotlin with properties and methods. The enum Color has a property rgb representing the color code. Each enum instance (RED, GREEN, BLUE) overrides the abstract method printInfo() to print a message including its rgb value. In main, we create a variable c assigned to Color.RED and call c.printInfo(), which outputs the message for RED. The execution table traces these steps, showing variable values and method calls. Key moments clarify why overriding methods per instance is useful and how properties are used. The quiz tests understanding of property values, method calls, and adding new enum instances. The snapshot summarizes the syntax and behavior of enums with properties and methods in Kotlin.