Ruby kind of vs instance of vs is a

Question

What is the difference  When should I use which  Why are there so many of them

User · Answer

What is the difference   From the documentation   -  Boolean  instance of  class Returns true if obj is an instance of the given class   and   -  Boolean  is a  class -  Boolean  kind of  class Returns true if class is the class of obj  or if class is one of the superclasses of obj or modules included in obj   If that is unclear  it would be nice to know what exactly is unclear  so that the documentation can be improved   When should I use which   Never  Use polymorphism instead   Why are there so many of them   I wouldn t call two  quot many quot   There are two of them  because they do two different things

User · Answer

kind of  and is a  are synonymous   instance of  is different from the other two in that it only returns true if the object is an instance of that exact class  not a subclass   Example     hello  is a  Object and  hello  kind of  Object return true because  hello  is a String and String is a subclass of Object  However  hello  instance of  Object returns false

User · Answer

It is more Ruby-like to ask objects whether they respond to a method you need or not  using respond to   This allows both minimal interface and implementation unaware programming    It is not always applicable of course  thus there is still a possibility to ask about more conservative understanding of  type   which is class or a base class  using the methods you re asking about

User · Answer

I also wouldn t call two many  is a  and kind of  are aliases of the same method   but if you want to see more possibilities  turn your attention to  class method   A   Class new B   Class new A  a  b   A new  B new b class  lt  A   true - means that b class is a subclass of A a class  lt  B   false - means that a class is not a subclass of A   Another possibility  Use  ancestors b class ancestors include  A   true - means that b class has A among its ancestors a class ancestors include  B   false - means that B is not an ancestor of a class

[ruby] Ruby: kind_of? vs. instance_of? vs. is_a?

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