How to choose between apply and with?

Answer

Both are scope functions, but they differ in object reference and return value.

apply

• Object Reference: this
• Return Value: The object itself.
• Use Case: Object configuration / initialization. "Apply these settings to the object."

Copy codeval intent = Intent().apply {
    action = Intent.ACTION_VIEW
    data = Uri.parse("https://google.com")
} // Returns the configured Intent

with

• Object Reference: this
• Return Value: The result of the lambda (last line).
• Use Case: Performing multiple operations on an object without returning it. "With this object, do these things."

Copy codeval length = with(person) {
    println(name)
    println(age)
    name.length // Returns this Int
}

Quick Rule

• Need the object back? Use apply.
• Need a result from the object? Use with (or run).