Access `self` of an object through the parameters

Question

Let's say I want to access an element of an array at a random index this way:

[1, 2, 3, 4].at(rand(4))

Is there a way to pass the size of the array like the following?

[1, 2, 3, 4].at(rand(le_object.self.size))

Why would I do that?--A great man once said: Science isn't about why, it is about why not.

Answer 1

Not recommended, but instance_eval would somehow work:

[1, 2, 3, 4].instance_eval { at(rand(size)) }

And you can also break out of tap:

[1, 2, 3, 4].tap { |a| break a.at(rand(a.size)) }

There's an open feature request to add a method that yields self and returns the block's result. If that makes it into Ruby, you could write:

[1, 2, 3, 4].insert_method_name_here { |a| a.at(rand(a.size)) }

Answer 2

No, you can't do that. Receiver of a method (that array) is not accessible by some special name at the call site. Your best bet is assigning a name to that object.

ary = [1, 2, 3, 4]
ary.at(rand(ary.size))

Of course, if all you need is a random element, then .sample should be used. Which does not require evaluation of any arguments at the call site and its self is the array.