Ruby assign do-block to array

Question

I'm a newbie Rails learner. I want to try out some ruby language features, e.g. shorten the following method:

def update(params)
  attrs = []
  params[:attributes].each do |attr_hash| 
    attr = Attribute.new attr_hash
    attrs.push attr
  end
  ...
end

like:

def update(params)
   attrs = fill_attrs_from_params params
   ...
end

def fill_attrs_from_params(params)
  attrs = params[:attributes].each do |attr_hash| 
    Attribute.new(attr_hash)
  end
end

The second doesn't work as the first one however. What do I miss here?

Edit: I couldn't really decide how the second one worked, the application went buggy, and I'm a beginner with rails debugging as well.

As you're not using attrs on fill_attrs_from_params you could just iterate over params[:attributes]. — Sebastián Palma
– Sebastián Palma, Commented Jun 7, 2017 at 17:29
Note also that "doesn't work" is not a precise enough error description for us to help you. What doesn't work? How doesn't it work? What trouble do you have with your code? Do you get an error message? What is the error message? Is the result you are getting not the result you are expecting? What result do you expect and why, what is the result you are getting and how do the two differ? Is the behavior you are observing not the desired behavior? What is the desired behavior and why, what is the observed behavior, and in what way do they differ? — Jörg W Mittag
– Jörg W Mittag, Commented Jun 7, 2017 at 18:25

Sergio Tulentsev · Accepted Answer · 2017-06-07 17:35:33Z

4

That's what .map is for

  attrs = params[:attributes].map do |attr_hash| 
    Attribute.new(attr_hash)
  end

.each is very versatile. With a bit of helper code, you can make it do anything. And that is its weakness. When you think to use .each, there's almost always a method on Enumerable that does the job better with less code (of course, except the obvious use case: performing an action on each element of a collection. Here you use .each.)

edited Jun 7, 2017 at 17:35

answered Jun 7, 2017 at 17:30

Sergio Tulentsev

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13 Comments

MattSom Over a year ago

So basically using .each does not return an array, only iterating it over?

Sergio Tulentsev Over a year ago

@MattSom: .each returns the original collection. Which might be what you want. But most often isn't.

Sergio Tulentsev Over a year ago

@Md.FarhanMemon: With the information available here, yes. I think, something is being done to attrs in the hidden code.

Sergio Tulentsev Over a year ago

@Md.FarhanMemon: question says "I want to shorten this piece of code" - the code in the answer is doing exactly the same thing, but shorter :)

Md. Farhan Memon Over a year ago

It also says "I'm a newbie" maybe a small chunk of memory can be saved here...allegedly :)

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