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ruby

What evaluates to false in Ruby?

false and nil evaluate to false in Ruby. Anything else? Please provide links to official/authoritative references.

2.0.0p247 :001 > if true ; puts 'TRUE' ; else puts 'FALSE' ; end
TRUE

2.0.0p247 :002 > if false ; puts 'TRUE' ; else puts 'FALSE' ; end
FALSE

2.0.0p247 :003 > if nil ; puts 'TRUE' ; else puts 'FALSE' ; end
FALSE

2.0.0p247 :004 > if 0 ; puts 'TRUE' ; else puts 'FALSE' ; end
TRUE

2.0.0p247 :005 > if [] ; puts 'TRUE' ; else puts 'FALSE' ; end
TRUE

2.0.0p247 :006 > if {} ; puts 'TRUE' ; else puts 'FALSE' ; end
TRUE

2.0.0p247 :007 > if '' ; puts 'TRUE' ; else puts 'FALSE' ; end
(irb):616: warning: string literal in condition
TRUE
Solution

  • false and nil are the only ones:

    http://www.ruby-doc.org/core-2.1.1/FalseClass.html

    Rails provides present? which also includes empty strings and empty arrays: http://api.rubyonrails.org/classes/Object.html#method-i-present-3F