method_defined?

method_defined?

ri

 ------------------------------------------------- Module#method_defined?
      mod.method_defined?(symbol)    => true or false
 ------------------------------------------------------------------------
      Returns  true  if the named method is defined by _mod_ (or its
      included modules and, if _mod_ is a class, its ancestors). Public
      and protected methods are matched.
 
         module A
           def method1()  end
         end
         class B
           def method2()  end
         end
         class C < B
           include A
           def method3()  end
         end
      
         A.method_defined? :method1    #=> true
         C.method_defined? "method1"   #=> true
         C.method_defined? "method2"   #=> true
         C.method_defined? "method3"   #=> true
         C.method_defined? "method4"   #=> false