CODEWITHSUNDEEP
rubymethods
Gabriel Mesquita
Gabriel Mesquita

Reputation: 2411

Why does calling 'is_a? Object' on a method return 'true'?

A ruby method is an Object. For example:

def method
  'does something'
end
method.is_a? Object #=> true

def method; end 
method.is_a? Object #=> true

Why is a method a Object?

Upvotes: 0

Views: 551

Answers (3)

Alexander Presber
Alexander Presber

Reputation: 6635

Like Ilya Konyukhov wrote, calling method.is_a?(Object) checks the return value of calling method, which would be "does something" and nil respectively - both of which are Objects.

Rubys methods are not objects per se but you can get an object representation of them using the Object#method method.

The funny part of your specific example is, that you unfortunately named your test method "method", thus overwriting your selfs method method.

Take a look at this example, where I named my method "test" instead:

def test; end

test.class.name          => "NilClass"

method(:test).class.name => "Method"

As you see, test is calling the method and everything after (e.g. is_a? or class.name) is called on the return value.

method(:test), however, returns an object representation (of class Method) of the method itself.

Upvotes: 2

steenslag
steenslag

Reputation: 80075

"Ruby' s methods are not objects in the way that strings, numbers and arrays are" (The Ruby Programming Language, Flanagan and Matsumoto, page 176). OP' s method name "method" is unfortunate; it makes it almost impossible to explain anything. If you need to treat a method as an object, there is the method method, which results in an instance of Class Method.

Upvotes: 1

Ilya Konyukhov
Ilya Konyukhov

Reputation: 2791

method.is_a?(Object)

can be rewritten as 

res = method
res.is_a?(Object)

So you call a method and ask if its result -- a String instance -- is an Object. For sure it is.

It can be easily verified with:

method.is_a?(String) # also returns true

Update:

If you want to check if a method itself an Object or not, you can do it with this code snippet:

def method2
  "some string"
end

method2_ref = Object.method(:method2) # #<Method: Object.method2>
method2_ref.is_a? Object # true
method2_ref.is_a? String # false

As it is mentioned in the comments, Method instance is also an Object.

Upvotes: 2

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