What apply() Looks Like

apply() is similar, though it is written as an extension function on T itself:

public inline fun <T> T.apply(block: T.() -> Unit): T {
    block()
    return this
}

Since apply() is an extension function of T, it can just call block() directly. this is already the correct receiver: the same object that apply() was called upon.

The other major difference is that with() returns the results of receiver.block(), while apply() returns this (the receiver).