With function behavior and use cases in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the with function in Kotlin?

The with function is used to call multiple methods or access properties on the same object without repeating the object name. It helps make code cleaner and easier to read.

beginner

How does the with function improve code readability?

It allows you to write code inside a block where the object is the receiver, so you don't need to repeat the object name for each call. This reduces clutter and makes the code look simpler.

intermediate

What is the return value of the with function?

The with function returns the result of the last expression inside its block.

beginner

Show a simple example of using with to configure a StringBuilder.

Example:

val result = with(StringBuilder()) {
    append("Hello")
    append(", ")
    append("World!")
    toString()
}
// result is "Hello, World!"

intermediate

When should you use with instead of apply or run?

Use with when you want to perform multiple operations on an object and return a value from the block, but you don't want to call it as an extension function. apply returns the object itself, and run is an extension function that returns the block result.

What does the with function take as its first argument?

A A Boolean condition

B A lambda with receiver

C A list of objects

D An object to operate on

The with function takes an object as its first argument and then a lambda block to operate on that object.

Inside the with block, how do you refer to the object passed in?

A Using <code>this</code> as the receiver

B Using the object name explicitly

C Using <code>it</code>

D Using a global variable

Inside the with block, the object is the receiver, so you can call its methods and properties directly using this implicitly.

What does with return?

A The object passed in

B The last expression inside the block

C Always <code>Unit</code>

D A Boolean value

The with function returns the value of the last expression inside its block.

Which of these is a typical use case for with?

A Filtering a list

B Creating a new object

C Configuring an object with multiple method calls

D Running code asynchronously

with is often used to call multiple methods on the same object to configure or build it.

How is with different from apply?

A <code>with</code> is not an extension function, <code>apply</code> is

B <code>with</code> returns the object, <code>apply</code> returns last expression

C <code>with</code> works only with strings, <code>apply</code> works with any object

D There is no difference

with is a regular function taking the object as an argument, while apply is an extension function called on the object.

Explain how the with function works in Kotlin and give an example of when you might use it.

Think about how you can avoid repeating the object name when calling multiple methods.

Compare with to apply and run in Kotlin. When would you choose with?

Focus on how each function is called and what they return.