What are Queues in ROR?

Queues are just like a waiting list. Imagine a scenario where you have to withdraw cash from the bank and you stand in a line waiting for your turn – this is a real-life example of a queue.

In Ruby, the implementation of Queue is similar to other object-oriented languages such as Java or Python.

Implementation

Ruby on Rails has a built-in class Queue that implements multi-producer, multi-consumer queues.

Some built-in methods in Ruby Queue Class include:

push() and pop()in Queue

• push() - inserts the element in the queue

• pop() - returns the element in the front of the queue and removes it from the queue

q1 = Queue.new
  q1.push(5)
  q1.push(6)
  puts q1.pop()

shift() in Queue

• returns and removes the front element of the queue

q1 = Queue.new
  q1.push(5)
  q1.push(6)
  puts q1.shift()

close() in Queue

• closes the queue permanently and does not allow any more push or pop operations

A closed queue cannot be re-opened.

q1 = Queue.new
  q1.push(5)
  q1.push(6)
  q1.close() //closes the queue
  puts q1.close() //checks whether the queue is closed or not.

clear() in Queue

• clears the queue and returns its size to zero

We can also re-insert objects into the queue.

q1 = Queue.new
  q1.push(5)
  q1.push(6)
  q1.clear()