Question

This is a pretty simple question.

def func1
  t2=Thread
    while true
      # if t2.alive?                   
      #   puts "GUI is running"
      # end
      puts Thread.t2.stop?
      puts "func1 at: #{Time.now}"
      sleep(1)
    end
end

t1=Thread.new{func1()}
t2=Thread.new{TheGUI()}
t1.join
t2.join

t2 is only declared later on in the code, so I am getting errors when trying to run this.
The error is ‘undefined local variable or method `t2”

How can I fix this without reordering my code?

Thanks

Answer 1

Your snippet is pretty small, so it’s hard to tell if your code is at top-level or in a class.

If t2 is supposed to be a global variable, note that Ruby prefixes global variables with a $: $t2.

If t2 is supposed to be a class member, note that Ruby prefixes member variables with a @: @t2.

Update

Your updated code is making an alias for the Thread class named t2. Check this output:

$ irb
irb(main):001:0> t2=Thread
=> Thread
irb(main):002:0> t2
=> Thread
irb(main):003:0> t2.methods()
=> ["private_class_method", "inspect", "name", "stop", "tap", "clone", "public_methods", "__send__", 
...
irb(main):004:0> Thread.methods()
=> ["private_class_method", "inspect", "name", "stop", "tap", "clone", "public_methods", "__send__", 

Furthermore, that t2 alias is only in force in the scope of the func1 function definition.

The simplest way to amend your code is probably to change func1 to take a parameter:

def func1(second_thread)
  while second_thread.alive?
    puts "GUI is running"
    sleep 1
  end
end

t2 = Thread.new {TheGUI()}
# pass the parameter to the function here
t1 = Thread.new(t2) { |thread| func1(thread) }
t1.join()
t2.join()