Ruby How to convert a string to boolean

Question

I have a value that will be one of four things  boolean true  boolean false  the string  true   or the string  false    I want to convert the string to a boolean if it is a string  otherwise leave it unmodified   In other words    true  should become true   false  should become false  true should stay true  false should stay false

User · Answer

If you use Rails 5  you can do ActiveModel  Type  Boolean new cast value    In Rails 4 2  use  ActiveRecord  Type  Boolean new type cast from user value    The behavior is slightly different  as in Rails 4 2  the true value and false values are checked  In Rails 5  only false values are checked - unless the values is nil or matches a false value  it is assumed to be true   False values are the same in both versions    FALSE VALUES    false  0   0    f    F    false    FALSE    off    OFF     Rails 5 Source  https   github com rails rails blob 5-1-stable activemodel lib active model type boolean rb

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In rails  I ve previously done something like this   class ApplicationController  lt  ActionController  Base            private def bool from value        ActiveRecord  Type  Boolean new type cast from database value    end   helper method  bool from          end   Which is nice if you re trying to match your boolean strings comparisons in the same manner as rails would for your database

User · Answer

I have a little hack for this one  JSON parse  false   will return false and JSON parse  true   will return true  But this doesn t work with JSON parse true    false   So  if you use something like JSON parse your value to s  it should achieve your goal in a simple but hacky way

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if value to s     true    true elsif value to s     false    false end

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Although I like the hash approach  I ve used it in the past for similar stuff   given that you only really care about matching truthy values - since - everything else is false - you can check for inclusion in an array   value    true   true   include  value    or if other values could be deemed truthy   value    1  true   1    true   include  value    you d have to do other stuff if your original value might be mixed case   value   value to s downcase     true    but again  for your specific description of your problem  you could get away with that last example as your solution

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Working in Rails 5  ActiveModel  Type  Boolean new cast  t           gt  true ActiveModel  Type  Boolean new cast  true        gt  true ActiveModel  Type  Boolean new cast true         gt  true ActiveModel  Type  Boolean new cast  1           gt  true ActiveModel  Type  Boolean new cast  f           gt  false ActiveModel  Type  Boolean new cast  0           gt  false ActiveModel  Type  Boolean new cast  false       gt  false ActiveModel  Type  Boolean new cast false        gt  false ActiveModel  Type  Boolean new cast nil          gt  nil

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Close to what is already posted  but without the redundant parameter   class String     def true          self to s downcase     true      end end   usage   do stuff    true   if do stuff true       do stuff end

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I ve frequently used this pattern to extend the core behavior of Ruby to make it easier to deal with converting arbitrary data types to boolean values  which makes it really easy to deal with varying URL parameters  etc   class String   def to boolean     ActiveRecord  Type  Boolean new cast self    end end  class NilClass   def to boolean     false   end end  class TrueClass   def to boolean     true   end    def to i     1   end end  class FalseClass   def to boolean     false   end    def to i     0   end end  class Integer   def to boolean     to s to boolean   end end   So let s say you have a parameter foo which can be    an integer  0 is false  all others are true  a true boolean  true false   a string   true    false    0    1    TRUE    FALSE   nil   Instead of using a bunch of conditionals  you can just call foo to boolean and it will do the rest of the magic for you   In Rails  I add this to an initializer named core ext rb in nearly all of my projects since this pattern is so common      EXAMPLES  nil to boolean        false true to boolean       true false to boolean      false 0 to boolean          false 1 to boolean          true 99 to boolean         true  true  to boolean     true  foo  to boolean      true  false  to boolean    false  TRUE  to boolean     true  FALSE  to boolean    false  0  to boolean        false  1  to boolean        true true to i             1 false to i            0

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h      true   gt true  true  gt true   false   gt false  false  gt false      true   true   false   false  map    e  h e         gt   true  true  false  false

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In Rails I prefer using ActiveModel  Type  Boolean new cast value  as mentioned in other answers here   But when I write plain Ruby lib  then I use a hack where  JSON parse  standard Ruby library  will convert string  true  to true and  false  to false  E g    require  json  azure cli response    az group exists --name derrentest       gt   true n  JSON parse azure cli response      gt  true  azure cli response    az group exists --name derrentesttt       gt   false n  JSON parse azure cli response      gt  false   Example from live application   require  json  if JSON parse  az group exists --name derrentest      az group create --name derrentest --location uksouth  end      confirmed under Ruby 2 5 1

User · Answer

Don t think too much   bool or string to s     true      So    true  to s     true     true  false  to s     true    false  true to s     true       true false to s     true      false   You could also add   downcase   if you are worried about capital letters

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def true  obj    obj to s downcase     true  end

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A gem like https   rubygems org gems to bool can be used  but it can easily be written in one line using a regex or ternary   regex example   boolean    var to s      true  i     0   ternary example   boolean   var to s eql   true     true   false   The advantage to the regex method is that regular expressions are flexible and can match a wide variety of patterns   For example  if you suspect that var could be any of  True    False    T    F    t   or  f   then you can modify the regex   boolean    var to s       Tt     i     0

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In a rails 5 1 app  I use this core extension built on top of ActiveRecord  Type  Boolean  It is working perfectly for me when I deserialize boolean from JSON string   https   api rubyonrails org classes ActiveModel Type Boolean html    app lib core extensions string rb module CoreExtensions   module String     def to bool       ActiveRecord  Type  Boolean new deserialize downcase strip      end   end end   initialize core extensions    config initializers core extensions rb String include CoreExtensions  String   rspec    spec lib core extensions string spec rb describe CoreExtensions  String do   describe   to bool  do      w 0 f F false FALSE False off OFF Off  each do  falsey string        it  converts   falsey string  to false  do         expect falsey string to bool  to eq false        end     end   end end

[ruby] Ruby: How to convert a string to boolean

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