How to find intersection between an array, and an array of arrays

Question

I have two arrays:

 array1 = [:key1, :key2]
 array2 = [[:key1,2],[:key2,8],[:key3,1]]

I would like to have an array of arrays in array2 whose :key... exists in array1. For example, for the above:

 result = [[:key1,2],[:key2,8]]

Answer 1

This works using a quick hash slice:

array1.zip(Hash[array2].values_at(*array1))
=> [[:key1, 2], [:key2, 8]]

It won't work if the key values in array2 ever repeat, because they'll stomp on the previous instances. Otherwise, if they don't repeat, this will be extremely fast, especially if array2 grows.

Answer 2

This satisfies your example:

array2.select {|key,value| array1.include?(key) }