Ruby On Rails: Can I call a class method from a class method?

Question

I need to know if I can call a class method from a class method and how.

I've got a class on my model and one of my class methods is getting long:

def self.method1(bar)
  # Really long method that I need to split
  # Do things with bar
end

So I want to split this method in 2 methods. Something like that

def self.method1(bar)
  # Do things with bar
  # Call to method2
end

def self.method2(bar)
  # Do things
end

Both of them must be class methods

How can I call this method2 from method1?

Thanks.

Of course you can do this call. Did you try it? Did you get an error? You might need to qualify it with `self.`: `self.method2(bar)`. — lurker, Jun 10 '18 at 14:25

score 1 · Accepted Answer · answered Jun 10 '18 at 14:27

This is answered here: Calling a class method within a class

To re-iterate:

def self.method1(bar)
  # Do things with bar
  # Call to method2
  method2( bar )
end

A full class example:

class MyClass
  def self.method1(bar)
    bar = "hello #{ bar }!"
    method2( bar )
  end

  def self.method2(bar)
    puts "bar is #{ bar }"
  end
end

MyClass.method1( 'Foo' )

score 1 · Answer 2 · answered Jun 10 '18 at 14:36

For you to understand what is going on, you've got to check the scope inside the class method.

class Foo
  def self.bar
    puts self
  end
end

Foo.bar
# => Foo

When Foo.bar is called, Foo is returned. Not an instance, but the class. That means you can access every class method of Foo inside the self.bar method.

class Foo
  def self.bar
    puts "bar was called"
    self.qux
  end

  def self.qux
    puts "qux was called."
  end
end

Foo.bar
# => bar was called
#    qux was called.

score 1 · Answer 3 · answered Jun 10 '18 at 15:53

self in the context of the class method is the class itself. So can access every class method defined in the current class. Examples above are very useful but I want to give you another one which is a little bit more clear (in my opinion):

class MyClass
   def self.method1
     p self
     puts "#{method2}"
   end

   def self.method2
     puts "Hello Ruby World!\n I am class method called from another class method!"
   end
 end

MyClass.method1
# => MyClass

# => Hello Ruby World!
     I am class method called from another class method!

Ruby On Rails: Can I call a class method from a class method?

3 Answers3