Solution:Step 1: Understand define_method inside loopMethods :start and :stop append their symbol to @events when called.Step 2: Trace method callstracker.start adds :start, tracker.stop adds :stop, tracker.start adds :start again.Step 3: Check final @events arrayThe array is [:start, :stop, :start]

[Solved] Consider this code: class Tracker def initialize @events = [] [:start, :stop].each do |event| define_method(event) { @events What is the output? | Ruby

Ruby - Advanced Metaprogramming

Consider this code:

class Tracker
  def initialize
    @events = []
    [:start, :stop].each do |event|
      define_method(event) { @events << event }
    end
  end
  def events
    @events
  end
end

tracker = Tracker.new
tracker.start
tracker.stop
tracker.start
puts tracker.events.inspect

What is the output?

A[]

B[:start, :start, :stop]

C[:stop, :start, :stop]

D[:start, :stop, :start]

Step-by-Step Solution

Solution:

Step 1: Understand define_method inside loop
Methods :start and :stop append their symbol to @events when called.
Step 2: Trace method calls
tracker.start adds :start, tracker.stop adds :stop, tracker.start adds :start again.
Step 3: Check final @events array
The array is [:start, :stop, :start].
Final Answer:
[:start, :stop, :start] -> Option D
Quick Check:
Methods append their symbol in call order [OK]

Quick Trick: define_method inside loop captures current event symbol [OK]

Common Mistakes:

Mixing order of events
Expecting empty array
Confusing symbols with strings

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Consider this code:

Step 1: Understand define_method inside loop

Step 2: Trace method calls

Step 3: Check final @events array

Final Answer:

Quick Check:

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