Ruby (Rails): remove whitespace from each array item

Adapting the approach you found, from working on a hash to working on an array:

[' c ', 'd', nil, 6, false].each { |a| a.strip! if a.respond_to? :strip! }
=> ["c", "d", nil, 6, false]

If you are using Rails, consider squish:

Returns the string, first removing all whitespace on both ends of the string, and then changing remaining consecutive whitespace groups into one space each.

yourArray.collect(&:squish)

If you don't mind first removing nil elements:

YourArray.compact.collect(&:strip) 

https://ruby-doc.org/core/Array.html#method-i-compact

This is what collect is for.

The following handles nil elements by leaving them alone:

yourArray.collect{ |e| e ? e.strip : e }

If there are no nil elements, you may use:

yourArray.collect(&:strip)

...which is short for:

yourArray.collect { |e| e.strip }

strip! behaves similarly, but it converts already "stripped" strings to nil:

[' a', ' b ', 'c ', 'd'].collect(&:strip!)
=> ["a", "b", "c", nil]

https://ruby-doc.org/core/Array.html#method-i-collect

https://ruby-doc.org/core/String.html#method-i-strip