Object declaration syntax in Kotlin - Step-by-Step Execution

Concept Flow - Object declaration syntax

Start

↓

Declare object with 'object' keyword

↓

Define properties and methods inside

↓

Use object directly without instantiation

↓

Access properties/methods

↓

End

This flow shows how Kotlin's object declaration creates a singleton object with properties and methods that can be used directly.

Execution Sample

Kotlin

object Logger {
    val prefix = "Log:"
    fun printMessage(msg: String) {
        println("$prefix $msg")
    }
}

Logger.printMessage("Hello")

Defines a singleton object Logger with a property and a method, then calls the method to print a message.

Execution Table

Step	Action	Evaluation	Result
1	Declare object Logger	Create singleton instance	Logger object created with prefix and printMessage
2	Access Logger.prefix	Retrieve value	"Log:"
3	Call Logger.printMessage("Hello")	Execute function	Prints: Log: Hello
4	End	No more code	Program ends

💡 Program ends after calling Logger.printMessage

Variable Tracker

Variable	Start	After 1	After 2	Final
Logger.prefix	undefined	"Log:"	"Log:"	"Log:"
Logger.printMessage	undefined	function defined	function defined	function remains

Key Moments - 3 Insights

Why don't we create an instance of Logger with 'new'?

Because Logger is declared with 'object', Kotlin creates a singleton automatically, so no 'new' is needed. See execution_table step 1.

How can we access properties inside the object?

We use the object name directly, like Logger.prefix, as shown in execution_table step 2.

What happens when we call Logger.printMessage?

The function runs and prints the message with the prefix, as shown in execution_table step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of Logger.prefix after step 2?

A "Log:"

B "Hello"

C undefined

D null

💡 Hint

Check the 'Evaluation' and 'Result' columns in execution_table row 2.

At which step does the program print the message 'Log: Hello'?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Prints' action in execution_table.

If we tried to create Logger with 'new Logger()', what would happen?

A It would create a new instance

B It would cause a compile error

C It would call printMessage automatically

D It would print 'Log: Hello'

💡 Hint

Recall that 'object' declarations are singletons and cannot be instantiated with 'new'.

Concept Snapshot

Kotlin object declaration syntax:
- Use 'object Name' to create a singleton
- Define properties and methods inside
- Access directly by Name.property or Name.method()
- No need to instantiate with 'new'
- Useful for single-instance utilities or holders

Full Transcript

This example shows how Kotlin's object declaration creates a singleton named Logger. The object has a property 'prefix' and a method 'printMessage'. When the program runs, Kotlin creates the Logger object automatically (step 1). We access the prefix property directly (step 2) and call the printMessage method (step 3), which prints the message with the prefix. The program ends after this (step 4). This shows that objects declared with 'object' are singletons and do not require instantiation with 'new'.