Class: Stud::Task

Inherits:
Object
  • Object
show all
Defined in:
lib/stud/task.rb

Overview

A Task spawns a thread to execute the given block. execution completion and result retrieval is done using the Task#wait method. A Task is run once and the thread exists upon block completion. A task and its underlying thread are not reusable.

Task does not provide a mean to force-interrupt a running task, it only provides the #stop! method to signal the task for a stop request. The task or code block can use the #stop? method to check for a stop request. Note that the #stop! and #stop? methods are thread safe.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args, &block) ⇒ Task

Returns a new instance of Task.



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# File 'lib/stud/task.rb', line 17

def initialize(*args, &block)
  # A queue to receive the result of the block
  # TODO(sissel): Don't use a queue, just store it in an instance variable.
  @queue = Queue.new

  @thread = Thread.new(@queue, *args) do |queue, *args|
    begin
      result = block.call(*args)
      queue << [:return, result]
    rescue => e
      queue << [:exception, e]
    end
  end # thread
end

Instance Attribute Details

#thread ⇒ Object (readonly)

provide access to the underlying thread if ever needed.



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# File 'lib/stud/task.rb', line 15

def thread
  @thread
end

Instance Method Details

#stop! ⇒ Object

stop! requests the task to stop. the Thread#wakeup method is also called so that a sleeping task is waked up and has a chance to verify the stop request using the #stop? method. also see Stud.stop!



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# File 'lib/stud/task.rb', line 51

def stop!
  Stud.stop!(@thread)
end

#stop? ⇒ Boolean Also known as: interrupted?

stop? returns true if this task stop! has been called See Stud.stop?

Returns:

  • (Boolean) —

    true if the stop! has been called



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# File 'lib/stud/task.rb', line 58

def stop?
  Stud.stop?(@thread)
end

#wait ⇒ Object, Exception

wait waits for the task thread to complete and return the block return value if the block raises an exception, this exception is propagated in this wait method.

Returns:

  • (Object, Exception) —

    block return value



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# File 'lib/stud/task.rb', line 36

def wait
  @thread.join
  reason, result = @queue.pop

  if reason == :exception
    #raise StandardError.new(result)
    raise result
  else
    return result
  end
end