rails - Finding intersections between multiple arrays

Question

I am trying to find the intersection values between multiple arrays.

for example

code1 = [1,2,3]
code2 = [2,3,4]
code3 = [0,2,6]

So the result would be 2

I know in PHP you can do this with array_intersect

I wanted to be able to easily add additional array so I don't really want to use multiple loops

Any ideas ?

Thanks, Alex

Answer 1

Use the & method of Array which is for set intersection.

For example:

> [1,2,3] & [2,3,4] & [0,2,6]
=> [2]

Answer 2

If you want a simpler way to do this with an array of arrays of unknown length, you can use inject.

> arrays = [code1,code2,code3]
> arrays.inject(:&)                   # Ruby 1.9 shorthand
=> [2]
> arrays.inject{|codes,x| codes & x } # Full syntax works with 1.8 and 1.9
=> [2]