Question

I am trying to log the average running time of 10 threads by using the inject method but it’s giving me this error:

undefined method `+' for #<Thread:0x10b211590 dead> (NoMethodError)
    from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/open-uri.rb:301:in `inject'
    from client_test.rb:13:in `each'
    from client_test.rb:13:in `inject'
    from client_test.rb:13

Here’s the code:

require 'open-uri'
program_start_time = Time.now
threads = 10.times.map do
  Thread.new do
    time = Time.now
    open('http://ca.yahoo.com/?p=us').read.length
    Time.now-time
  end
end

threads.map &:join
puts threads.inject() { |sum, e| sum + e.value}.to_f / threads.size
puts Time.now - program_start_time

Answer 1

You need to provide an initial value for inject in this case, since if you don’t, the initial value is simply the first element in the array:

puts threads.inject(0) { |sum, e| sum + e.value}.to_f / threads.size