Ruby threads and variable

Question

Why the result is not from 1 to 10, but 10s only?

require \'thread\'

def run(i)
  puts i
end

while true
  for i in 0..10
    Thread.new{ run(i)}
  end
  sl         


        

Answer 1

@DavidGrayson is right.

You can see here a side effect in for loop. In your case i variable scope is whole your file. While you are expecting only a block in your for loop as a scope. Actually this is wrong approach in idiomatic Ruby. Ruby gives you iterators for this job.

(1..10).each do |i|
   Thread.new{ run(i)}
end

In this case scope of variable i will be isolated in block scope what means for each iteration you will get new local (for this block) variable i.