In Kotlin, scope functions are a set of functions that allow you to apply some operations on an object within a certain scope. These functions provide a convenient way to execute a block of code on an object and return either the object itself or a modified version of the object.

Kotlin has five scope functions:

Apply:

• It takes an object and executes a block of code on it, then returns the object itself. It is useful when you want to modify an object's properties in a concise way.

data class Person(var name: String, var age: Int, var address: String)

fun main() {
    val person = Person("John Doe", 30, "123 Main St")
    val modifiedPerson = person.apply { this
        name = "Jane Doe"
        age = 25
    }
}

With:

• The context object is available as a receiver (this).
• The return value is the lambda result

fun main() {
    val person = Person("John Doe", 30, "123 Main St")
    with(person) {
        println("The person's name is $name, they are $age years old, and they live at $address.")
    }
}

Also:

• The context object is available as an argument (it).
• The return value is the object itself.

fun main() {
    val text: String? = "hello"
    val result = text?.also {
        println("The original string was $it")
    }?.toUpperCase()
    println(result)
}

Let:

• The context object is available as an argument (it).
• The return value is the lambda result.
• let is often used to execute a code block containing non-null values

val str: String? = null  
//processNonNullString(str)       // compilation error: str can be null
val length = str?.let { 
    println("let() called on $it")    
}

Run:

• The context object is available as a receiver (this).