Add element to an array if it's not there already

@Coorasse has a good answer, though it should be:

my_array | [item]

And to update my_array in place:

my_array |= [item]

You can use Set instead of Array.

You don't need to iterate through my_array by hand.

my_array.push(item1) unless my_array.include?(item1)

Edit:

As Tombart points out in his comment, using Array#include? is not very efficient. I'd say the performance impact is negligible for small Arrays, but you might want to go with Set for bigger ones.