How to map and remove nil values in Ruby

Question

I have a map which either changes a value or sets it to nil. I then want to remove the nil entries from the list. The list doesn\'t need to be kept.

Thi

Answer 1

If you wanted a looser criterion for rejection, for example, to reject empty strings as well as nil, you could use:

[1, nil, 3, 0, ''].reject(&:blank?)
 => [1, 3, 0] 

If you wanted to go further and reject zero values (or apply more complex logic to the process), you could pass a block to reject:

[1, nil, 3, 0, ''].reject do |value| value.blank? || value==0 end
 => [1, 3]

[1, nil, 3, 0, '', 1000].reject do |value| value.blank? || value==0 || value>10 end
 => [1, 3]

Answer 2

each_with_object is probably the cleanest way to go here:

new_items = items.each_with_object([]) do |x, memo|
    ret = process_x(x)
    memo << ret unless ret.nil?
end

In my opinion, each_with_object is better than inject/reduce in conditional cases because you don't have to worry about the return value of the block.