Ruby - ignore "exit" in code

Question

Consider this code:

class Bar
  def initialize
    puts 'Hi from class Bar.'
    exit
  end
end


class Foo
  def initialize
    loop {
      case $stdin.gets.chomp
      when 'foo'
        puts 'Hi from class Foo.'
      when 'bar'
        Bar.new
      end
    }
  end
end

Can I ignore the exit in class Bar somehow?

It terminates my loop. I don't want that.

Note - the real code base is much larger and more complicated than that. But it boils down to this question whether I can ignore exit() or not.

pts · Accepted Answer · 2014-01-01 11:30:22Z

6

loop {
  begin
    Bar.new
  rescue SystemExit
    p $!  #: #<SystemExit: exit>
  end
}

This will print #<SystemExit: exit> in an infinite loop, without ever exiting.

edited Jan 1, 2014 at 11:30

answered Dec 31, 2013 at 23:23

pts

88.7k26 gold badges117 silver badges203 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

rogerdpack Over a year ago

does this prevent the script from exiting?

pts Over a year ago

@rogerdpack: Yes, it does. Updated my answer.

shevy Over a year ago

Thanks, I think this is the best solution to handle exits from other code.

user2864740 · Accepted Answer · 2014-01-01 10:38:20Z

2

One hackish way to define an exit method in context:

class Bar; def exit; end; end

This works because exit in the initializer will be resolved as self.exit¹. In addition, this approach allows using the object after it has been created, as in: b = B.new.

But really, one shouldn't be doing this: don't have exit (or even puts) there to begin with.

(And why is there an "infinite" loop and/or user input in an intiailizer? This entire problem is primarily the result of poorly structured code.)

¹ Remember Kernel#exit is only a method. Since Kernel is included in every Object, then it's merely the case that exit normally resolves to Object#exit. However, this can be changed by introducing an overridden method as shown - nothing fancy.

edited Jan 1, 2014 at 10:38

answered Dec 31, 2013 at 23:22

user2864740

62.5k15 gold badges159 silver badges234 bronze badges

5 Comments

the Tin Man Over a year ago

While exit can be overridden, should it is the real question. I can imagine some nasty bugs down the road for that codebase. Exit has a specific purpose and expected behavior and changing it would be really irritating.

user2864740 Over a year ago

@theTinMan I agree. A added emphasis to "shouldn't" .. at least the behavior is confined to B or a subclass.

shevy Over a year ago

"> don't have exit (or even puts) there to begin with" - What if you are not in control over code written by someone else?

shevy Over a year ago

Interesting solution but not clean - I do not want to redefine exit in my project. I merely want other classes to not exit when they think they should want to do so - I don't want to allow them to exit when they think I should exit. The earlier solution to rescue SystemExit seems clearer and cleaner than redefining or aliasing exit.

user2864740 Over a year ago

@user722915 You don't need to redefine exit in the project: it is only changed in the B class. And I agree it's not "clean", but this entire problem isn't clean and the fundamental broken design should be fixed. This is the only way I know of to use the result of the method call/initializer. Catching the exception unwinds the stack, which makes B.new (read: this code) seem like even more of a joke if instances of B are never meant to be used.

Collectives™ on Stack Overflow

Ruby - ignore "exit" in code

2 Answers 2

3 Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related