Adding elements to array into nested loop

Question

I am trying to add elements to an array, and then push it to a hash. I need following output

{:jan=>"jan", :feb=>"jan", :mar=>"jan", :apr=>"jan", :cont=>["j", "a", 
 "n"]}
{:jan=>"feb", :feb=>"feb", :mar=>"feb", :apr=>"feb", :cont=>["f", "e", 
 "b"]}
{:jan=>"mar", :feb=>"mar", :mar=>"mar", :apr=>"mar", :cont=>["m", "a", 
 "r"]}
{:jan=>"apr", :feb=>"apr", :mar=>"apr", :apr=>"apr", :cont=>["a", "p", 
 "r"]}

Here is my code:

arr = ['jan', 'feb', 'mar', 'apr']
cont = []

arr.each do |f|
 cont.clear
 f.split('').each do |t|
  cont << t
 end

 hash = {jan: f, feb: f, mar: f, apr: f, cont: cont}
 trending_repos.push(hash)
end

puts trending_repos

In the first iteration, it pushes the array that I want to see at the last. Here is the output:

{:jan=>"jan", :feb=>"jan", :mar=>"jan", :apr=>"jan", :cont=>["a", "p", 
 "r"]}
{:jan=>"feb", :feb=>"feb", :mar=>"feb", :apr=>"feb", :cont=>["a", "p", 
 "r"]}
{:jan=>"mar", :feb=>"mar", :mar=>"mar", :apr=>"mar", :cont=>["a", "p", 
 "r"]}
{:jan=>"apr", :feb=>"apr", :mar=>"apr", :apr=>"apr", :cont=>["a", "p", 
 "r"]}

You are clearing the const each iteration. This clears, adds to it, then clear... You to rearrange the order you are doing things. — ForeverZer0
– ForeverZer0, Commented Jul 29, 2018 at 19:17
@ForeverZer0yes because I need to empty array before nested each. I have figure out. Instead of cont.clear I need to move cont = [] inside first loop. — rob111
– rob111, Commented Jul 29, 2018 at 19:20
I see now, I was thinking the end for the inner-loop was the close of the outer block. :P — ForeverZer0
– ForeverZer0, Commented Jul 29, 2018 at 19:51
Clearing the array was clearing all of them, so they would all be equal to the result of the last iteration. — ForeverZer0
– ForeverZer0, Commented Jul 29, 2018 at 19:54

Cary Swoveland · Accepted Answer · 2018-07-30 06:20:59Z

4

This is all you need to do.

keys = arr.map(&:to_sym)
  #=> [:jan, :feb, :mar, :apr]
arr.map { |s| { **keys.product([s]).to_h, cont: s.chars } }
  #=> [{:jan=>"jan", :feb=>"jan", :mar=>"jan", :apr=>"jan", :cont=>["j", "a", "n"]},
  #    {:jan=>"feb", :feb=>"feb", :mar=>"feb", :apr=>"feb", :cont=>["f", "e", "b"]},
  #    {:jan=>"mar", :feb=>"mar", :mar=>"mar", :apr=>"mar", :cont=>["m", "a", "r"]},
  #    {:jan=>"apr", :feb=>"apr", :mar=>"apr", :apr=>"apr", :cont=>["a", "p", "r"]}]

See this article for a good discussion of Ruby's double-splat operator for hashes. In short, { **{ a: 1 }, b: 2 } #=> {:a=>1, :b=>2} is analogous to the single-splat operator for arrays: [*[1,2],3] #=> [1,2,3].

edited Jul 30, 2018 at 6:20

answered Jul 29, 2018 at 20:27

Cary Swoveland

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2 Comments

Amadan Over a year ago

Or arr.map { |s| {**arr.map { |k| [k.to_sym, s] }.to_h, cont: s.chars }} to avoid hardcoding.

Cary Swoveland Over a year ago

@Amadan, good suggestion. I implemented a little differently (then edited again, unable to resist the double-splat).

rob111 · Accepted Answer · 2018-07-29 19:27:23Z

1

I have figured out whats wrong with my code. I need to move declaration of array cont inside first loop. Here is correct code.

arr = ['jan', 'feb', 'mar', 'apr']

arr.each do |f|
 cont = []
 f.split('').each do |t|
   cont << t
 end

 hash = {jan: f, feb: f, mar: f, apr: f, cont: cont}
 trending_repos.push(hash)
end

answered Jul 29, 2018 at 19:27

rob111

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1 Comment

ForeverZer0 Over a year ago

Yes, another reference/value issue.

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