Question

In a very simple program trying to use “each” I get the error : sum.rb:16: undefined method `each’ for # (NoMethodError)

I get the same error using “each” various ways: the one shown below was copied directly from the Class:Matrix from ruby-doc.org.

# create State database using matrix
require 'matrix'

State=Matrix[ [3,1,4,4,6,2,8,12,6,2],
        [6,2,4,13,25,21,11,22,9,3,],
        [6,20,27,34,22,14,12,11,2,5],
        [6,28,17,23,31,18,15,9,18,12],
        [9,18,11,13,8,27,10,14,24,11],
        [3,9,7,16,9,15,28,24,29,21],
        [5,8,4,7,17,14,19,30,33,4],
        [7,17,23,9,5,9,22,21,12,21,],
        [7,14,25,22,16,10,19,15,12,11],
        [5,16,7,3,6,3,9,8,1,5] ]

State.each { |e| puts e }

This must be simple/obvious but I can’t figure it out. (I’ve already done a variety of things with the State matrix that work out as expected.)

Answer 1

Ruby 1.8.7 will return the problem you are seeing. The Matrix object in 1.8.7 doesn’t have an each method.

Upgrading to a recent version, either 1.9.2 or 1.9.3 will fix the problem.