arity() public

Returns an indication of the number of arguments accepted by a method. Returns a nonnegative integer for methods that take a fixed number of arguments. For Ruby methods that take a variable number of arguments, returns -n-1, where n is the number of required arguments. For methods written in C, returns -1 if the call takes a variable number of arguments. 

   class C
     def one;    end
     def two(a); end
     def three(*a);  end
     def four(a, b); end
     def five(a, b, *c);    end
     def six(a, b, *c, &d); end
   end
   c = C.new
   c.method(:one).arity     #=> 0
   c.method(:two).arity     #=> 1
   c.method(:three).arity   #=> -1
   c.method(:four).arity    #=> 2
   c.method(:five).arity    #=> -3
   c.method(:six).arity     #=> -3

   "cat".method(:size).arity      #=> 0
   "cat".method(:replace).arity   #=> 1
   "cat".method(:squeeze).arity   #=> -1
   "cat".method(:count).arity     #=> -1
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