CODEWITHSUNDEEP
rubyarrayspass-by-reference
Amey
Amey

Reputation: 8548

How to work around the unavailibilty of passing by reference in ruby?

My problem is around the fact that I cannot pass by reference in Ruby. I have two functions searching and get_title_ids.

I have two arrays in searching

(1) title (2) href
which needs to be updated.

def searching
    title = []
    href = []
    (0..20).step(10) do |i|
        prev= title.length
        title, href = get_title_ids(i, title, href) ## <<-- Should have just done "get_title_ids(i, title, href)"
        ## something which on next iteration will increase the ids and hrefs
        puts "\nthe title lenght is #{title.length} and href length is #{href.length}\n"
        assert_operator prev,:<,title.length,"After scrolling to bottom no new jobs are getting added" 
    end
end

def get_title_ids (start_from=0, title=[], href=[])
    #Part of code which can store all links and titles of jobs displayed
    (start_from..(titles.length-1)).each do |i|
            unless titles[i].text.chomp
                title << titles[i].text.chomp
                href << titles[i].attribute("href")
            end     
        end
    end
    return [title, href] ### <<---- this is what messed it up
end

The problem is I am unable to push new elements into the arrays title and href that have been defined in searching.

Each time I call get_title_ids i do not want to gather data that I had previously gathered(hence the start_form).

My problem is not memory but time. So i am not too concerned about the data being duplicated when I call the get_title_ids function as compared to the fact that I have to waste time scrapping data that I already scrapped in the previous for loop.

So does any one know how to hack the pass by reference in Ruby.

EDIT

SO from reading the questions below turns out I dint need to perform the return from get_title_ids. And then it all worked.

Upvotes: 0

Views: 91

Answers (2)

Hunter McMillen
Hunter McMillen

Reputation: 61520

Even if a reference type object is passed by value, it is still referring to the same object in memory. If this were not the case then the example below would not work.

example:

> def searching
>   title = []
>   href = []
>   test(title, href)
>   puts "Title: #{title.inspect} Href: #{href.inspect}"
> end

> def test(title, href)
>   title << "title1"
>   title << "title2"
>   href << "www.title1.com"
>   href << "www.title2.com"
> end

> searching

Title: ["title1", "title2"] Href: ["www.title1.com", "www.title2.com"]

Upvotes: 1

Sergio Tulentsev
Sergio Tulentsev

Reputation: 230461

Arrays in ruby are most certainly passed by reference (well, technically, they are passed by value, but that value is a pointer to the array). Observe:

def push_new ary
  ary << 'new element'
end

a = ['first element']
push_new a
a # => ["first element", "new element"]

Upvotes: 2

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