Built-in 'with' type method that returns the object it was called on

Question

In Kotlin, there is the apply method:

inline fun <T> T.apply(block: T.() -> Unit): T (source)

Calls the specified function block with this value as its receiver and returns this value.

This allows you to configure an object like the following:

val myObject = MyObject().apply {
  someProperty = "this value"
  myMethod()
}

myObject would be the MyObject after the apply {} call.

Groovy has the with method, which is similar:

public static <T,U> T with(U self, 
  @DelegatesTo(value=DelegatesTo.Target.class,target="self",strategy=1)
  Closure<T> closure
)

Allows the closure to be called for the object reference self.

...

And an example from the doc:

def b = new StringBuilder().with {
  append('foo')
  append('bar')
  return it
}
assert b.toString() == 'foobar'

The part with the Groovy method is always having to use return it to return the delegate of the with call, which makes the code considerably more verbose.

Is there an equivalent to the Kotlin apply in Groovy?

Answer 1

The function is called tap and is part of Groovy 2.5. See discussions about the naming in merge request.

Other than that, only foo.with{ bar=baz; it } can be used. You can retrofit your own doto, tap, apply, ... via metaprogramming.