Also function behavior and use cases in Kotlin - Step-by-Step Execution

Concept Flow - Also function behavior and use cases

Start with an object

↓

Call also { block }

↓

Inside block: 'it' refers to object

↓

Perform side actions (e.g., print, modify)

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Return original object

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Continue with original object

The also function lets you run extra code on an object and then returns the original object unchanged.

Execution Sample

Kotlin

val number = 5
val result = number.also {
    println("Number is $it")
}.times(2)
println(result)

Prints the number using also, then multiplies it by 2 and prints the result.

Execution Table

Step	Code Line	Action	Value of 'it'	Result/Output
1	val number = 5	Assign 5 to number	-	number = 5
2	number.also { println("Number is $it") }	Call also on number; inside block print	5	Prints: Number is 5
3	.times(2)	Multiply original number by 2	-	Result = 10
4	println(result)	Print final result	-	Prints: 10
5	-	End of execution	-	-

💡 Execution stops after printing the final result 10.

Variable Tracker

Variable	Start	After also block	After times(2)	Final
number	5	5	5	5
result	-	-	10	10

Key Moments - 2 Insights

Why does the also function return the original object and not the block's last expression?

Because also is designed to perform side effects without changing the object; see execution_table step 2 where the block prints but the original number is returned.

What does 'it' refer to inside the also block?

'it' refers to the original object the also function is called on, as shown in execution_table step 2 where 'it' is 5.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is printed inside the also block?

A Number is 10

B Number is 5

C Result is 10

D No output

💡 Hint

Check the 'Result/Output' column at step 2 in execution_table.

At which step does the variable 'result' get the value 10?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Value of result' in variable_tracker after times(2).

If the also block modified 'it' to 7, what would be the value of 'result' after times(2)?

A 14

B 7

C 10

D 5

💡 Hint

also returns the original object unchanged, see key_moments about return behavior.

Concept Snapshot

also function syntax:
object.also { it -> /* side actions */ }

- Runs block with 'it' as the object
- Returns original object unchanged
- Useful for side effects like logging or debugging
- Allows chaining without breaking flow

Full Transcript

The also function in Kotlin lets you run extra code on an object without changing it. When you call also on an object, it passes the object as 'it' inside the block. You can do things like print or modify properties inside the block. After the block runs, also returns the original object unchanged. This is useful when you want to add side effects like logging but keep using the original object in a chain of calls. For example, number.also { println("Number is $it") }.times(2) prints the number and then multiplies it by 2. The execution steps show the value of variables and outputs at each stage, helping you see how also works step-by-step.