Ruby mapping array into hash

Question

I have a 2D array with each row like:

['John', 'M', '34']

I want to map into an array of Hash with each hash like:

{:Name=>"John", :Gender=>"M", :Age=>"34"}

Is there an elegant way of doing that?

Answer 1

array_of_rows.map { |n,g,a| { Name: n, Gender: g, Age: a } }

or

array_of_rows.map { |row| %i{Name Gender Age}.zip(row).to_h }

They produce the same result, so pick the one you find clearer. For example, given this input:

array_of_rows = [
  ['John', 'M', '34'],
  ['Mark', 'M', '49']
]

either expression will yield this output:

[{:Name=>"John", :Gender=>"M", :Age=>"34"}, 
 {:Name=>"Mark", :Gender=>"M", :Age=>"49"}]

Answer 2

You could try using zip and then to_h (which stands for to hash)

For example:

[:Name, :Gender, :Age].zip(['John', 'M', '34']).to_h
=> {:Name=>"John", :Gender=>"M", :Age=>"34"}

Read more about zip here

And read about to_h here

Answer 3

people = [['John', 'M', '34']]
keys = %i{Name Gender Age}

hashes = people.map { |person| keys.zip(person).to_h }
# => [{:Name=>"John", :Gender=>"M", :Age=>"34"}]

Basically the way I turn combine two arrays into a hash (one with keys, one with values) is to use Array#zip . This can turn [1,2,3] and [4,5,6] into [[1,4], [2,5], [3,6]]

This structure can be easily turned into a hash via to_h

Answer 4

array_of_rows = [
  ['John', 'M', '34'],
  ['Mark', 'M', '49']
]

keys = ['Name', 'Gender', 'Age']

[keys].product(array_of_rows).map { |k,v| k.zip(v).to_h }
  #=> [{"Name"=>"John", "Gender"=>"M", "Age"=>"34"},
  #    {"Name"=>"Mark", "Gender"=>"M", "Age"=>"49"}]

or

keys_cycle = keys.cycle
array_of_rows.map do |values|
  values.each_with_object({}) { |value, h| h[keys_cycle.next]=value }
do

Answer 5

Here is one more way to do this

array_of_rows = [
  ['John', 'M', '34'],
  ['Mark', 'M', '49']
]

keys = [:Name, :Gender, :Age]

array_of_rows.collect { |a| Hash[ [keys, a].transpose] }
#=>[{:Name=>"John", :Gender=>"M", :Age=>"34"}, {:Name=>"Mark", :Gender=>"M", :Age=>"49"}]