How can I “extract” values from a multidimensional array in a smart way?

Question

I am using Ruby on Rails 3.2.2 and Ruby 1.9.2.

Given the following multidimensional Array:

[[\"value1\", \"value1_other\"], [\"value2\",         


        

Answer 1

>> array = [["value1", "value1_other"], ["value2", "value2_other"], ["value3", "value3_other"]]
=> [["value1", "value1_other"], ["value2", "value2_other"], ["value3", "value3_other"]]
>> array.map { |v| v[0] }
=> ["value1", "value2", "value3"]

Answer 2

You can use Array#collect to execute a block for each element of the outer array. To get the first element, pass a block that indexes the array.

arr.collect {|ind| ind[0]}

In use:

arr = [["value1", "value1_other"], ["value2", "value2_other"], ["value3", "value3_other"]]
=> [["value1", "value1_other"], ["value2", "value2_other"], ["value3", "value3_other"]]
arr.collect {|ind| ind[0]}
=> ["value1", "value2", "value3"]

Instead of {|ind| ind[0]}, you can use Array#first to get the first element of each inner array:

arr.collect(&:first)

For the &:first syntax, read "Ruby/Ruby on Rails ampersand colon shortcut".

Answer 3

arr = [["value1", "value1_other"], ["value2", "value2_other"], ["value3", "value3_other"]]

Solution1 = arr.map {|elem| elem.first}

Solution2 = arr.transpose[0]