Why concurrency matters in Ruby - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new thread that prints 'Hello from thread!'.

Ruby

thread = Thread.new { puts [1] }
thread.join

Drag options to blanks, or click blank then click option'

A"Hello from thread!"

BHello from thread!

Cprint 'Hello from thread!'

Dputs Hello from thread!

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the string.

Using print instead of puts inside the thread block.

In Ruby, strings must be quoted. To print the message, we use puts with a quoted string.

2fill in blank

medium

Complete the code to start two threads that each print a different message.

Ruby

t1 = Thread.new { puts [1] }
t2 = Thread.new { puts [2] }
t1.join
t2.join

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A"Thread 1 running"

B"Thread 2 running"

C"Running thread"

D"Thread running"

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the string.

Using the same message for both threads.

The first thread prints "Thread 1 running" and the second prints "Thread 2 running".

3fill in blank

hard

Fix the error in the code to safely increment a shared counter using a Mutex.

Ruby

counter = 0
mutex = Mutex.new
threads = []
5.times do
  threads << Thread.new do
    mutex.[1] do
      counter += 1
    end
  end
end
threads.each(&:join)
puts counter

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Asynchronize

Bunlock

Cwait

Dlock

Attempts:

3 left

💡 Hint

Common Mistakes

Using lock without unlocking.

Using unlock directly.

Using wait which is not a Mutex method.

To safely access shared data in Ruby threads, use Mutex#synchronize which locks and unlocks automatically.

4fill in blank

hard

Fill both blanks to create a thread that sleeps for 2 seconds and then prints a message.

Ruby

thread = Thread.new do
  sleep [1]
  puts [2]
end
thread.join

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A2

B"Done sleeping"

C"Sleeping done"

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around the number 2.

Not quoting the message string.

The thread sleeps for 2 seconds, then prints the message 'Done sleeping'.

5fill in blank

hard

Fill all three blanks to create a thread-safe counter increment using Mutex and threads.

Ruby

counter = 0
mutex = Mutex.new
threads = []
10.times do
  threads << Thread.new do
    mutex.[1] do
      counter [2] 1
    end
  end
end
threads.each(&:join)
puts counter [3] 10

Drag options to blanks, or click blank then click option'

Asynchronize

B+=

C==

Dlock

Attempts:

3 left

💡 Hint

Common Mistakes

Using lock without unlocking.

Using = instead of +=.

Using = instead of == for comparison.

Use synchronize to lock the counter increment safely, += to add 1, and == to check the final value.