Clean way to push results of multiple methods into an array

Question

I have the following Ruby code, which calls the same function multiple times with different arguments, and pushes the results into a common array.

people_relations = []
people.zip(people_addresses).map do |person, address|
  people_relations.push(createRelation(person, address))
end
people.zip(people_ph_numbers).map do |person, phone_number|
  people_relations.push(createRelation(person, phone_number))
end
people.zip(people_aliases).map do |person, _alias|
  people_relations.push(createRelation(person, _alias))
end

def createRelation(e1, e2)
  [true, false].sample ? CurrentRelation.new(e1, e2) : PastRelation.new(e1, e2)
end

This code works just fine, but I feel like this is not the idiomatic Ruby way of doing things, and can be improved by compressing the code into less lines or made to look cleaner.

Is there a better way to write the code that appears above?

What's the meaning of the ternary with [true, false].sample? — Sebastián Palma
– Sebastián Palma, Commented Jul 23, 2018 at 1:42
@SebastianPalma It's my way of randomly choosing between creating a PastRelation or CurrentRelation object. — JavascriptLoser
– JavascriptLoser, Commented Jul 23, 2018 at 1:46
@SebastianPalma The definition of the function is already there, down the bottom. — JavascriptLoser
– JavascriptLoser, Commented Jul 23, 2018 at 1:54

Sebastián Palma · Accepted Answer · 2018-07-23 02:15:46Z

2

You could create an array that contains all the people "attributes" you're going to use, and with Enumerable#each_with_object you can assign an initial array to fill with the result of each call to createRelation():

attributes = [people_addresses, people_ph_numbers, people_aliases]
relations = people.each_with_object([]).with_index do |(person, memo), index|
  attributes.each do |attribute|
    memo << createRelation(person, attribute[index])
  end
end

edited Jul 23, 2018 at 2:15

answered Jul 23, 2018 at 2:06

Sebastián Palma

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1 Comment

Maycon Seidel Over a year ago

this is very very very hard to read and understand, but contemplates the answer like a charm. Should be consider the correct answer.

Simple Lime · Accepted Answer · 2018-07-23 02:28:32Z

1

I'd probably go with a transpose -> flat_map solution for this myself, for instance given:

def CreateRelation(person, relationship)
  if [true, false].sample
    "#{person} is currently related to #{relationship}"
  else
    "#{person} used to be related to #{relationship}"
  end
end

people = ['Person 1', 'Person 2', 'Person 3']
addresses = ['Person 1 Address', 'Person 2 Address', 'Person 3 Address']
phone_numbers = ['Person 1 Phone', 'Person 2 Phone', 'Person 3 Phone']
aliases = ['Person 1 AKA', 'Person 2 AKA', 'Person 3 AKA']

We can stick those 4 arrays into a single array and then transpose them, so the first element of each ends up in an array with each other, the second in another, and the last in a third:

[people, addresses, phone_numbers, aliases].transpose # => [
#  ["Person 1", "Person 1 Address", "Person 1 Phone", "Person 1 AKA"],
#  ["Person 2", "Person 2 Address", "Person 2 Phone", "Person 2 AKA"],
#  ["Person 3", "Person 3 Address", "Person 3 Phone", "Person 3 AKA"]]

and then you can flat_map those by calling CreateRelation:

result = [people, addresses, phone_numbers, aliases].transpose.flat_map do |person, *relations|
  relations.map { |relationship| CreateRelation(person, relationship) }
end
#["Person 1 used to be related to Person 1 Address",
# "Person 1 used to be related to Person 1 Phone",
# "Person 1 used to be related to Person 1 AKA",
# "Person 2 is currently related to Person 2 Address",
# "Person 2 used to be related to Person 2 Phone",
# "Person 2 is currently related to Person 2 AKA",
# "Person 3 is currently related to Person 3 Address",
# "Person 3 used to be related to Person 3 Phone",
# "Person 3 used to be related to Person 3 AKA"]

Or, at that point you could stick with just iterating and pushing, if you don't want to map/flat_map.

The more I think about it, the more I think I'd go with transpose -> each_with_object, instead of flat_map...less "create an array and then throw it away", I'll leave this with flat_map though because it is another option and @Sebastian Palma has each_with_object covered.

edited Jul 23, 2018 at 2:28

answered Jul 23, 2018 at 2:11

Simple Lime

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2 Comments

JavascriptLoser Over a year ago

I liked this one most because it is the most concise and "artistic" solution. Thanks!

engineersmnky Over a year ago

@JavascriptLoser As an aside since I have no overt objections to this answer Array#zip can accept any number of Arrays so people.zip(addresses, phone_numbers, aliases) would have the same result as [people, addresses, phone_numbers, aliases].transpose

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