In the following array, how would I find the position of the product with id = 71?
[[[#<Product id: 71>, #<BigDecimal:x>], 0], [[#<Product id: 73>, #<BigDecimal:x>], 1]]
Alternatively, if I have @product = Product.find(71), how would I then find that this object is associated with the number 0 and not 1 in the above array?
You can use Array#index with block, with block arguments deconstruction (here using symbols instead of your custom objects):
arr = [[[:a, :b], 5], [[:c, :d], 7]]
# => [[[:a, :b], 5], [[:c, :d], 7]]
arr.index{|((a, b), c)| c == 7}
# => 1
arr.index{|((a, b), c)| b == :a}
# => nil
arr.index{|((a, b), c)| b == :b}
# => 0
If you are interested in particular element, rather than its index, just use find instead of index (block argument would be the same).
