How deeply does Kotlin in Action, 2E cover with?

Explains invocation syntax, receiver access, implicit this, return value, and the analogy with extension functions.

With

with is a Kotlin standard-library scope function that executes a block with an object as its receiver and returns the block result.

with is a Kotlin standard-library function for performing several operations on one object without repeating its name. It passes the object as the receiver of a lambda, so the lambda can call the receiver’s methods directly. section 5.4.1

Build an alphabet with StringBuilder

fun alphabet() = with(StringBuilder()) { for (letter in 'A'..'Z') { append(letter) } append("\nNow I know the alphabet!") toString() } Here, StringBuilder is the receiver. Inside the lambda, append and toString can be called without repeating stringBuilder or writing this. The final expression, toString(), becomes the result returned by with. section 5.4.1

Use the receiver explicitly when clarity requires it:

this.append(letter) identifies the receiver directly; append(letter) uses the same receiver implicitly. section 5.4.1
with is a library function rather than a special language statement, although trailing-lambda syntax makes it resemble one. section 5.4.1
A lambda with a receiver resembles an extension function because both provide direct access to a receiver’s members. section 5.4.1

How Kotlin in Action, 2E covers it

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Related concepts

lambda with receiveruses · A lambda with receiver is a lambda whose function type designates one parameter as an implicit receiver, allowing the lambda body to access that receiver's members without qualification.
lambdauses · A lambda is a language construct that defines an unnamed function or callable, often as a value.
applycontrasts with · apply is a Kotlin standard-library scope function that executes a lambda with the receiver as its implicit receiver and returns that receiver.

This explainer was generated by Manning's knowledge graph from the text of Kotlin in Action, 2E. The section links point to the parts of the book it draws on.