When any record has certain attribute, change parent status

I want to change the status of a Job-record, after the status of any of its children (Jobdetails) is set to true.

Basically the code should be something like:

if every Job.jobdetail.status == true
  Job.status = true
end

the problem is, that i dont know how to check for any. Of course i know the where-statement in rails but I am not sure how to express the "any" without an each iteration, which wont work in this case i guess. Everytime after I update the Jobdetails, I want to check if the other Jobdetails are "done" too. Imagine the function like a progressbar. If every sub-job is done, change the status of the main-job to done. How do I achieve this?

thanks in regards.