How to make Rails.logger.debug print hash more readable

Question

I'm using Rails.logger.debug print variables for debugging purposes. The issue is it prints hashes in an impossible to read format (can't distinguish keys from values). For example, I add the following lines to my code base

#code_base.rb
 my_hash = {'a' => 'alligator', 'b'=>'baboon'}
 Rails.logger.debug my_hash

Then I launch my rails app and type

  tail -f log/development.log 

But when my_hash gets printed, it looks like

  bbaboonaalligator

The key and values are scrunched up, making it impossible to parse. Do you guys know what I should do to fix this?

Urumchi

Answer 1

Nevermind, I found the answer to my own question. I need to use

my_hash = {'a' => 'alligator', 'b'=>'baboon'}
Rails.logger.debug "#{my_hash.inspect}"

Then, it looks like

{"b"=>"baboon", "a"=>"aligator"}

Urumchi

Answer 2

It's even easier to read it when you use to_yaml eg:

logger.debug my_hash.to_yaml

Which is an easy to read format over multiple lines. The inspect method simply spews out a string.

Atheistic

Great tip here! to_yaml also creates a string, but it's formatted with \n and indentation so it's much easier to skim a large or nested hash… If you're trying to log a hash-like object (say, params), you may end up with ivars clogging the data you're interested in. Turn it into a normal hash first and then turn that into yaml: logger.debug params.to_hash.to_yaml – Gaikwar

Answer 3

my_hash = {'a' => 'alligator', 'b'=>'baboon'}
logger.debug "#{my_hash}"

Then, it looks like

{"b"=>"baboon", "a"=>"aligator"}

do not need inspect

Whitcher

Answer 4

There is an another way to do this. There is a ruby built in module pp.rb that is Pretty-printer for Ruby objects.

non-pretty-printed output by p is:

#<PP:0x81fedf0 @genspace=#<Proc:0x81feda0>, @group_queue=#<PrettyPrint::GroupQueue:0x81fed3c @queue=[[#<PrettyPrint::Group:0x81fed78 @breakables=[], @depth=0, @break=false>], []]>, @buffer=[], @newline="\n", @group_stack=[#<PrettyPrint::Group:0x81fed78 @breakables=[], @depth=0, @break=false>], @buffer_width=0, @indent=0, @maxwidth=79, @output_width=2, @output=#<IO:0x8114ee4>>

pretty-printed output by pp is:

#<PP:0x81fedf0
 @buffer=[],
 @buffer_width=0,
 @genspace=#<Proc:0x81feda0>,
 @group_queue=
  #<PrettyPrint::GroupQueue:0x81fed3c
   @queue=
    [[#<PrettyPrint::Group:0x81fed78 @break=false, @breakables=[], @depth=0>],
     []]>,
 @group_stack=
  [#<PrettyPrint::Group:0x81fed78 @break=false, @breakables=[], @depth=0>],
 @indent=0,
 @maxwidth=79,
 @newline="\n",
 @output=#<IO:0x8114ee4>,
 @output_width=2>

Liselisetta

This would pretty-print the hash to a console, but how do you send pp output to a log file? – Amphictyon

Answer 5

For more complex objects even with ActiveRecord, this could be achieved with a JSON.pretty_generate

Rails.logger.debug JSON.pretty_generate(my_hash.as_json)

Rancell