Let function with safe calls in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the let function do in Kotlin?

The let function executes a block of code on the object, passing the object as a parameter ('it') to the block. When used with safe calls (?.), it only executes if the object is not null.

beginner

How do safe calls work with let in Kotlin?

Safe calls (?.) allow you to call let only if the object is not null, preventing null pointer exceptions.

beginner

Example: What will this code print?<br><pre>val name: String? = null
name?.let { println("Name is $it") }</pre>

Nothing will be printed because name is null, so let block is skipped.

intermediate

Why use let with safe calls instead of a simple if check?

let with safe calls makes code concise and readable by combining null check and action in one expression.

intermediate

What is the type of the parameter inside the let block when used with safe calls?

Inside the let block, the parameter is the non-nullable version of the original object.

What happens when you use ?.let on a null object?

A A null pointer exception occurs

B The <code>let</code> block runs with null

C The <code>let</code> block is skipped

D The program crashes

Using ?.let means the block runs only if the object is not null. If null, it skips safely.

Inside a let block called with safe call, the object is:

A Nullable

B Non-nullable

C Always a String

D An Int

The object inside let is smart cast to non-nullable because the block runs only if the object is not null.

Which operator is used to safely call let on a nullable object?

A ?.

B ?:

C ::

D !!

The safe call operator ?. calls let only if the object is not null.

What is the main benefit of using let with safe calls?

A It forces null pointer exceptions

B It makes code longer

C It disables null safety

D It combines null check and action in one concise expression

let with safe calls helps write concise, readable code by combining null check and action.

What will this code print?<br>

val age: Int? = 25
age?.let { println("Age is $it") }

A Age is 25

B Nothing

C Age is null

D Error

Since age is not null, the let block runs and prints the age.

Explain how the let function works with safe calls in Kotlin and why it is useful.

Think about how safe calls prevent errors and how let helps run code only when the object is not null.

Write a simple Kotlin example using a nullable variable with ?.let to print its value only if it is not null.

Use a nullable variable and call <code>?.let</code> with a print inside the block.