is a very beginner question but even tho i cannot find any helpful documentation online.
I'm working on Discourse application which is Ruby on Rails + Ember based.
I need to print out in my terminal (not in my view!) the value of a variable.
I try:
debugger
put varName
logger.debug varName
but none of them print anything in my console.
What i need to do is stop my console from running and print a value.
Like debugger; would do in javascript.
How can i do this simple task?
1) not sure if this change anything but the .rb file i try to debug is a "services".
2) yes, i read about pry, i installed it and add to my file:
require 'pry'
binding.pry
But i don't see anything happening in the console.
Related
I'm wondering if it's possible to start a Byebug session giving a starting point from a Rails console. I know I can insert a byebug statement wherever I want and start debugging, but I'd like to do something like this:
Byebug.start do
# entry point
User.find(12).problematic_method
end
Thanks.
I opened the class and override the problematic_method inside the Rails console and added the byebug statement where I wanted it. This way I don't have to change the running production code (I forgot to mention above I want to debug in production).
This workaround will be enough for my purposes. The only problem is that you don't have the debug code listing available for that method, but its fine.
That is not possible. What you can do, is write your code inside a .rb file and debug that file/script using byebug.
I want to get some lines printed in irb opened through rails console. I have seen a lot of SO questions of how to achieve it. But I get nothing in the irb.
below is the code--
def show
puts 'in show method'
#post = Feed.find_by_id params[:id]
puts #post.inspect
redirect_to root_path unless #post.present?
end
now I have opened server by command rails server. Also, In another terminal I gave the command rails console, it opened the irb prompt. when in browser I run localhost:3000/posts/82 it gives the correct post, but nothing is shown in the console. What step am I missing? I want to print something in the console when a particular method is called.
Best way to debug is to use the debugger command.
If you are using ruby 2.0 or above, you have to use the gem 'byebug' and if you are using 1.9 or below, then gem ruby-debug
then, when you run your server in development mode, your server will stop when it reaches the debugger allowing you to see your objects' state and modify them (much better than simply using puts
The program will stop in the same window that your server runs.
Some basic commands:
c continues the execution until next debugger is found
n runs the next command. If it is a function executes the
function
s step into the next command. If it is a
function, you will get into the function and see the variables
display expression on every step display the result of the
expression you write (very useful when debugging loops)
undisplay expression_number stops displaying the expresion
display shows all the expressions being displayed
list Displays the source code being executed
help shows the available commands help
command_name shows detailed info about a command
More info about debugging: http://guides.rubyonrails.org/debugging_rails_applications.html
The puts 'in show method' in line 2 won't show the output in rails console. Instead it shows the output in the same terminal where you did rails server. They might be lost with so much of output, so try to find it there itself.
Use Rails.logger.debug "in show method" etc.
In the second tab in terminal tail log/development.log like this
$ cd rails_app_root
$ tail -f log/development.log
or
$ cd rails_app_root
$ less +F log/development.log
There you will find all the output from the console.
Try to use Rails.logger
Rails.logger.info "Some debugging info I want to see in my
development log.------#{#post.inspect}"
It will print #post value in log file.
I am a big fan of puts debugging. e.g;
def index
method = Kernel.instance_method(:method)
p method.bind(request).call(:headers).source_location
#users = User.all
end
The above snippet helps you find where the method is implemented:
Processing by UsersController#index as */*
["/Users/aaron/git/rails/actionpack/lib/action_dispatch/http/request.rb", 201]
You can find more cool puts debugging here.
I have a Rails application, and I'm trying to export data, but directly through Pry because I only need to do it once.
Is this possible with Pry? I looked at the documentation but doesn't seem like there's an easy way to dump console data anywhere.
I have a hash, with nested hashes/objects, which I need to send over to a 3rd party for work with an API. They need a dump of the data so they can set up the receiving end of my call. I'm just going to do this in Ruby now, but it would have made more sense to dump the data through PRY, rather than edit my ruby object to dump the data, which I only need once.
If you can start the server from a local command-line, or SSH to the host and run an instance there, you can use Pry for this. Basically you need to add these lines to your code at the appropriate place:
require 'pry-debugger'; binding.pry
which will stop your code and put you at the Pry prompt. At that point you can enter something like:
require 'json'
File.write('test.data', hash.to_json)
Read the Pry.debugger documentation for information about using Pry with remote Rails sessions, which might work better for you.
You can also export any string into a file (here output.txt):
x = 'something funky'
.echo '#{x}' > output.txt
Just be careful with quotes in the string. These may lead to problems in the shell.
Sometimes when I'm working in the rails console, I find I want to step through a particular method (from my rails app) in the debugger. In the past I have done this by temporarily adding a debugger statement to the source code of the method, then calling that method from the console.
Is there a way I can "step into" a method from the console, without editing its source code?
This would be particularly nice on a shared development server, so that I wouldn't need to throw in random debugger statements with vi and remember to remove them later.
I tried the following but not surprisingly it doesn't work:
$ rails c --debugger
=> Debugger enabled
Loading development environment (Rails 3.2.13)
irb(main):001:0> def startdebug
irb(main):002:1> debugger
irb(main):003:1> MyModel.last.my_method
irb(main):004:1> end
=> nil
irb(main):005:0> startdebug
It says
*** No sourcefile available for (irb)
And soon I end up stepping through irb code rather than my_method.
mhm this sound a bit like metaprogramming for me, you may inject a debugging method at runtime in your model, which will add the debugging statement just before the method call so you can inspect the call as needed, like:
m = MyModel.last
m.class.send(:define_method, :debug_my_method){debugger; my_method}
m.debug_my_method
this should do on the irb (just tested it on may rails console)
How do I debug the rails gems? I've just found the beauty of ruby-debug and am real excited, but I want to step through the routing code in action_controller, but the debugger isn't set up at this time, it seems like it's just skipping over my "debugger" calls in action_controller/routing/route_set.rb for example.
What am I missing?
I just tested this with Rails 2.3.4. I added a 'debugger' line to the call method in vendor/rails/actionpack/lib/action_controller/routing/route_set.rb, ran 'rdebug script/server', browsed to a page, and it stopped at the correct line.
You can also use a class/method breakpoint; you'll need to step through the first few lines of the app until you're past the require 'action_controller' line, and then enter: b ActionController::Routing::RouteSet.call.
Or you can try setting a breakpoint based on the file name and line number.