How to chain a method call to a `do ... end` block in Ruby?

Question

I'm doing the following:

array_variable = collection.map do |param|
  some value with param
end
return array_variable.compact

Can I call map and compact in one statement somehow, so I can return the result instantly?

I'm thinking on something like this (it may be invalid, however):

array_variable = block_code param.compact 
# block_code here is a method for example which fills the array

Karyokinesis

Your question is unclear. You can only call methods on objects, but blocks aren't objects, so you can't call methods on them. You can reify a block into a Proc object, and then you can call methods on it; but Procs don't have a compact method. (What does it even mean to "compact a block"?) – Bolingbroke

I'm surely not all clear with Ruby at the moment. I want to compact the array object, but I'm filling it inside the do block. I did not say what I was thinking is good, I only wanted to clarify that I want to fill and compact the array in once. Like a function composition. – Karyokinesis

So, you are asking whether you can call a method on the return value of a method? – Bolingbroke

No. Stefan clarified the issue. – Karyokinesis

Now I am even more confused. You accepted an answer as correct which shows you how to call a method (in this case compact) on the return value of another method (in this case map), but that is not what you are asking? Then, what is it you are asking and why did you accept an answer that answers a question you are not asking? – Bolingbroke

A method which uses a do..end block. Yes, in this context this is what I was asking for, my bad. – Karyokinesis

I understood the question immediately and find it very useful. – Genius

Answer 1

yes, you can call a method here.

In your case,

array_variable = collection.map do |param|
  # some value with param
end.compact

OR

array_variable = collection.map{ |param| some value with param }.compact

As pointed out by @Stefan, assignment is not required, you can directly use return and if that's the last line of method you can omit return too..

Vetchling

In your case, you are calling compact on the return value of map (which is an Array), while the question asks to "call method on a block". Now, I have no idea what "call method on a block" even means, but you are definitely calling compact on an Array. – Bolingbroke

yes ofcourse, it very much depends on the return type, since map returns an array and compact belongs to it it is good to go but not always..that's why I mentioned 'yes you can call a method here' – Vetchling

@JörgWMittag I think you are slightly making an unnecessary quarrel, Md.FarhanMemon realized instantly what I want, surely you did as well. My question title was wrong, I admit. But yes, I want to compact the result of the block, as it clearly mapped the return values into the array. – Karyokinesis

Note that the OP wants to return the result, so the assignment to array_variable is superfluous. Simply return collection.map { ... }.compact (you can even omit return if this is the method's last statement) – Christianize

I personally am annoyed by the end.compact syntax, because the letters kind of run together, so it's easy to miss on a quick scan. My view is that there's nothing wrong with a multi-line block delimited by curly braces. – Sunderland