I type next on binding.pry or byebug to step over to the next line. I use step to step into the procedure. How do I step BACK a line?
I've been looking through documentation with no luck. Help greatly appreciated. Thanks.
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11You don't step back. While there are some debuggers that do "time travel," allowing you to step backwards, Ruby does not have such a debugger. Once an instruction has been executed you can't go back to a state before it was executed.Jordan Running– Jordan Running2015-05-05 20:15:27 +00:00Commented May 5, 2015 at 20:15
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damn. alright, well, thanks for clearing that up. what languages do support 'time travel' ?jamesdlivesinatree– jamesdlivesinatree2015-05-05 20:30:49 +00:00Commented May 5, 2015 at 20:30
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Here's a discussion on Programmers Stack Exchange about "reverse debugging" that names a few technologies and gives some good background on the challenges involved: programmers.stackexchange.com/questions/181527/…Jordan Running– Jordan Running2015-05-05 20:33:05 +00:00Commented May 5, 2015 at 20:33
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4 Answers
You can make use of up & down methods in binding.pry
see here:
Frame number: 0/64
From: /Users/johnmair/ruby/rails_projects/personal_site/app/controllers/posts_controller.rb @ line 7 PostsController#index:
5: def index
6: @posts = Post.all
=> 7: binding.pry
8: end
[1] pry(#<PostsController>)> show-stack
Showing all accessible frames in stack (65 in total):
--
=> #0 index <PostsController#index()>
#1 [method] send_action <ActionController::ImplicitRender#send_action(method, *args)>
#2 [method] process_action <AbstractController::Base#process_action(method_name, *args)>
#3 [method] process_action <ActionController::Rendering#process_action(*arg1)>
<... clipped ...>
[2] pry(#<PostsController>)> up
Frame number: 1/64
Frame type: method
From: /Users/johnmair/.rvm/gems/ruby-2.0.0-p0/gems/actionpack-3.2.8/lib/action_controller/metal/implicit_render.rb @ line 4 ActionController::ImplicitRender#send_action:
3: def send_action(method, *args)
=> 4: ret = super
5: default_render unless response_body
6: ret
7: end
[3] pry(#<PostsController>)>
1 Comment
Goulven
Exactly what I needed! You need to install the pry-stack-explorer gem though: github.com/pry/pry-stack_explorer
There isn't a step back or undo step command listed on this Pry Cheat Sheet. I would suggest ctrl + c (x2), ctrl + d, the get back into your container and hit the binding pry again.
Comments
Compromise solution is re-entering into execution of previous pieces of code with pry-moves.
For example if you stopped inside of Controller's action:
def index
list = Orders.for_user(current_user)
=> binding.pry
end
And now you want to understand why is list empty? - You can run:
> debug Orders.for_user(current_user)
and check what's happening there
Why we have to use compromises? The problem is that ruby environment doesn't keep whole state of system on each step. Presumably it is because most probably you still will use external systems (e.g. by API calls) which may change their internal state and you can't automatically "roll it back".
