Optionality in Ruby: compacting collections

A handy trick for building parameters with optional arguments is to build a parameter collection allowing the optional values to be nil then run #compact on them. We’ve seen some hints of this, but lets look at the technique more closely.

maybe = [3, nil].sample

[ 1, 2, maybe, 4].
    compact.
    append(5)

  { :foo => 1,
    :bar => 2,
    :baz => maybe,
    :qux => 4
  }.compact.
    merge(wat: 5)

Not much else to be said, really. #compact is defined on Array, Hash, and Enumerable so you’ll likely find it on many other collections. It only works with nil values, but you can generalize the technique with Enumerable#select.