Is there equivalent for PHP's print_r in Ruby / Rails? - ruby-on-rails

Question

In PHP you can do:
print_r($var) or vardump($var)
which prints "human-readible" information about variable.
Is there equivalent functions / helpers for those in Ruby / Rails ?

Answer 1

In Rails templates you can do
<%= debug an_object %>
and it will do nice HTML PRE output.

Answer 2

Try using pp.
You will need to require it in scripts (or in irb if your .irbc doesn't already do this):
require 'pp'
Then you can 'PrettyPrint' an object thus:
pp object

Answer 3

Instead of requiring 'pp' and using pp, you can simply do
p object
Tested example
require 'pp'
class A
def initialize
#a = 'somevar'
#b = [1,2,3]
#c = {'var' => 'val'}
end
end
a = A.new
pp a # Gives -> #<A:0x2c6d048 #a="somevar", #b=[1, 2, 3], #c={"var"=>"val"}>
p a # Gives -> #<A:0x2c6d048 #a="somevar", #b=[1, 2, 3], #c={"var"=>"val"}>. No need to require 'pp'

Answer 4

There's the method inspect which helps. Sometimes calling the to_s method on an object will help (to_s returns a string representation of the object). You can also query methods, local_variables, class_variables, instance_variables, constants and global_variables.
p ['Hello',"G'day",'Bonjour','Hola'].inspect
# >> "[\"Hello\", \"G'day\", \"Bonjour\", \"Hola\"]"
p ['Hello',"G'day",'Bonjour','Hola'].to_s
# >> "HelloG'dayBonjourHola"
p Array.new.methods
# >> ["select", "[]=", "inspect", "compact"...]
monkey = 'baboon'
p local_variables
# >> ["monkey"]
class Something
def initialize
#x, #y = 'foo', 'bar'
##class_variable = 'gorilla'
end
end
p Something.class_variables
# >> ["##class_variable"]
s = Something.new
p s.instance_variables
# >> ["#x", "#y"]
p IO.constants
# >> ["TRUNC", "SEEK_END", "LOCK_SH"...]
p global_variables
# >> ["$-d", "$\"", "$$", "$<", "$_", "$-K"...]

Answer 5

I know this is an old post, but it is the first thing that Google pops up when searching for "Ruby equivalent of PHP print_r". I'm using Ruby in the command line mode, and there's really not a very good equivalent. "pp" is ok for fairly simple structures, but as soon as you start nesting hashes in arrays in hashes in more arrays, it turns into a jumble pretty fast. Since I haven't found a good emulation of print_r, I wrote one myself. It's good enough for my purposes, not overly complicated and I thought I'd share it to save other people some headache. Compare the output with the real PHP print_r
def print_r(inHash, *indent)
#indent = indent.join
if (inHash.class.to_s == "Hash") then
print "Hash\n#{#indent}(\n"
inHash.each { |key, value|
if (value.class.to_s =~ /Hash/) || (value.class.to_s =~ /Array/) then
print "#{#indent} [#{key}] => "
self.print_r(value, "#{#indent} ")
else
puts "#{#indent} [#{key}] => #{value}"
end
}
puts "#{#indent})\n"
elsif (inHash.class.to_s == "Array") then
print "Array\n#{#indent}(\n"
inHash.each_with_index { |value,index|
if (value.class.to_s == "Hash") || (value.class.to_s == "Array") then
print "#{#indent} [#{index}] => "
self.print_r(value, "#{#indent} ")
else
puts "#{#indent} [#{index}] => #{value}"
end
}
puts "#{#indent})\n"
end
# Pop last indent off
8.times {#indent.chop!}
end
Here's an example (made messy on purpose to show why the PHP print_r is so nice):
carTools = [ "Socket Set", "Combination Wrenches", "Oil Filter puller", "Brake Compressor" ]
houseTools =[ "Circular Saw", "Miter Saw", "Drill" ]
garageItems = Hash["Car1" => "Ford Mustang", "Car2" => "Honda Civic", "Bike1" => "IronHorse"]
garageItems["Tools"] = Hash["Car Tools" => carTools, "House Tools" => houseTools]
constructionSupplies = Hash["Plywood" => ["3/4\" T&G Plywood Sheets", "1/2\" Plywood Sheets"],
"Boards" => ["2x4s", "2x6s", "Engineered I-Joists"],
"Drywall" => ["4x8 1/2\" Sheetrock", "Mesh tape", "Paper tape", "Joint compount"]]
carParts = Hash["Mustang" => ["Clutch", "Transmission", "3.55 Ring & Pinion Gears", "Differential", "30# Injectors", "Pro-M 77mm MAF"]]
garageItems["Supplies"] = ["Oil", "WD40", constructionSupplies, carParts, "Brake Fluid"]
print_r(garageItems)
Output of print_r (actually comprehensible by a human):
Hash
(
[Car1] => Ford Mustang
[Car2] => Honda Civic
[Bike1] => IronHorse
[Tools] => Hash
(
[Car Tools] => Array
(
[0] => Socket Set
[1] => Combination Wrenches
[2] => Oil Filter puller
[3] => Brake Compressor
)
[House Tools] => Array
(
[0] => Circular Saw
[1] => Miter Saw
[2] => Drill
)
)
[Supplies] => Array
(
[0] => Oil
[1] => WD40
[2] => Hash
(
[Plywood] => Array
(
[0] => 3/4" T&G Plywood Sheets
[1] => 1/2" Plywood Sheets
)
[Boards] => Array
(
[0] => 2x4s
[1] => 2x6s
[2] => Engineered I-Joists
)
[Drywall] => Array
(
[0] => 4x8 1/2" Sheetrock
[1] => Mesh tape
[2] => Paper tape
[3] => Joint compount
)
)
[3] => Hash
(
[Mustang] => Array
(
[0] => Clutch
[1] => Transmission
[2] => 3.55 Ring & Pinion Gears
[3] => Differential
[4] => 30# Injectors
[5] => Pro-M 77mm MAF
)
)
[4] => Brake Fluid
)
)

Answer 6

Check out the guide for debugging rails:
http://guides.rubyonrails.com/debugging_rails_applications.html
hints:
script/console is great to try stuff in the context of your app
script/server --debugger to start the server with a debugger turned on, you can then use 'debug' in your code to break into an interactive shell

Answer 7

One approach I lean on a lot is this:
logger.debug "OBJECT: #{an_object.to_yaml}"
Easy to read, although it can get a little unwieldy for large objects.

Answer 8

Guess I'm a little late to this, but what about logger.info [debug|warning]? Use this from Controllers and Models. It will show up in your log files (development.log when in dev mode); and the above mentioned <%= debug("str: " + str) %> for views.
These aren't exact answers to your questions but you can also use script/console to load your rails app in to an interactive session.
Lastly, you can place debugger in a line of your rails application and the browser will "hang" when your app executes this line and you'll be able to be in a debug session from the exact line your placed your debugger in the source code.