Conditional key/value in a ruby hash

Question

Is there a nice (one line) way of writing a hash in ruby with some entry only there if a condition is fulfilled? I thought of

{:a => \'a\', :b => (\'b\         


        

Answer 1

This one is nice for multiple conditionals.

(
  hash = {:a => 'a'}.tap {|h|
    h.store( *[(:b if condition_b), 'b'] )
    h.store( *[(:c if condition_c), 'c'] )
  }
).delete(nil)

Note that I chose nil as the "garbage" key, which gets deleted when you're done. If you ever need to store a real value with a nil key, just change the store conditionals to something like:

(condition_b ? :b : garbage_key)

then delete(garbage_key) at the end.

This solution will also keep existing nil values intact, e.g. if you had :a => nil in the original hash, it won't be deleted.