What is a elegant way in Ruby to tell if a variable is a Hash or an Array

Question

To check what  some var is  I am doing a  if  some var class to s     Hash     I am sure there is a more elegant way to check if  some var is a Hash or an Array

User · Accepted Answer

You can just do    some var class    Hash   or also something like    some var is a  Hash    It s worth noting that the  is a   method is true if the class is anywhere in the objects ancestry tree  for instance    some var is a  Object       gt  true   the above is true if  some var is an instance of a hash or other class that stems from Object  So  if you want a strict match on the class type  using the    or instance of  method is probably what you re looking for

User · Answer

Hash      some var    gt  return Boolean   this can also be used with case statement  case  some var when Hash        when Array        end

User · Answer

Usually in ruby when you are looking for  type  you are actually wanting the  duck-type  or  does is quack like a duck     You would see if it responds to a certain method     some var respond to   each    You can iterate over  some var because it responds to  each  If you really want to know the type and if it is Hash or Array then you can do     Hash    Array   include   some var class      gt  check both through instance class  some var kind of  Hash        gt  to check each at once  some var is a  Array       gt  same as kind of

User · Answer

In practice  you will often want to act differently depending on whether a variable is an Array or a Hash  not just mere tell  In this situation  an elegant idiom is the following   case item   when Array     do something   when Hash     do something else end   Note that you don t call the  class method on item

User · Answer

I use this    var respond to   keys    It works for Hash and ActiveSupport  HashWithIndifferentAccess

User · Answer

irb main  005 0 gt     class   gt  Hash irb main  006 0 gt     class   gt  Array

User · Answer

You can use instance of   e g   some var instance of  Hash

User · Answer

If you want to test if an object is strictly or extends a Hash  use   value      value is a  Hash     value is a  Array     gt  true   But to make value of Ruby s duck typing  you could do something like   value      value respond to          gt  true   It is useful when you only want to access some value using the value  key  syntax      Please note that Array new  key   will raise a TypeError

User · Answer

First of all  the best answer for the literal question is  Hash      some var   But the question really should have been answered by showing how to do duck-typing here  That depends a bit on what kind of duck you need    some var respond to   each pair    or   some var respond to   has key     or even   some var respond to   to hash    may be right depending on the application

[ruby] What is a elegant way in Ruby to tell if a variable is a Hash or an Array?

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