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One of Pry's killer features is its ability to display source code for methods and classes. Pry does this without relying on any external utilities. Source browsing is an invaluable tool when you are coming to grips with a new code base and it comes into its own when the library you are exploring has little or no documentation.

View method and class source code with show-source

The show-source command is capable of showing source code for classes/modules and methods. Simply typing show-source method_name will pull the source for the method and display it with syntax highlighting. As a convenience, Pry looks up both instance methods and class methods using this syntax, with priority given to instance methods.

Alternatively, if you pass in a class (or module), Pry will show the source for that class, e.g. show-source MyClass.

The ri method syntax is also supported. This enables you to specify both a context and a method. In ri syntax C#m specifies the instance method m on the class C. And obj.m selects the method (or class method) m on the object obj.

Note that the context and method are resolved dynamically (with respect to the current context) and so constructions such as MyClass.new.my_method are valid.

Also note that methods defined inside Pry itself are also viewable using show-source.

The following options are supported:

  • Use the -s option to select the super method. You can repeat -ss to get to the super method's super method.
  • Use the -l option to include line numbers
  • Use the -b option to include line numbers, but start numbering at 1 (useful when used with play)
  • Use the -a option to show source for all definitions and monkey-patches of the module/class

Aliases: $, show-method

Example (recorded) :

[1] pry(main)> cd Pry
[2] pry(Pry):1> show-source rep

From: /home/curacao/.gem/ruby/1.9.3/gems/pry-0.9.11.4/lib/pry/pry_instance.rb @ line 252:
Owner: Pry
Visibility: public
Number of lines: 8

def rep(target=TOPLEVEL_BINDING)
  target = Pry.binding_for(target)
  result = re(target)

  Pry.critical_section do
    show_result(result)
  end
end
[3] pry(Pry):1>

Example (recorded): showing a class' source

[1] pry(main)> show-source Pry

From: /home/curacao/.gem/ruby/1.9.3/gems/pry-0.9.11.4/lib/pry/pry_instance.rb
Number of lines: 737

class Pry

  attr_accessor :input
  attr_accessor :output
  attr_accessor :commands
  attr_accessor :print
:                 

Example (recorded): with ri syntax

[1] pry(main)> require 'set'
=> true
[2] pry(main)> show-source Set#replace -l

From: /opt/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/set.rb @ line 132:
Owner: Set
Visibility: public
Number of lines: 10

132: def replace(enum)
133:   if enum.instance_of?(self.class)
134:     @hash.replace(enum.instance_variable_get(:@hash))
135:   else
136:     clear
137:     merge(enum)
138:   end
139: 
140:   self
141: end
[3] pry(main)>

Example (recorded): methods defined inside Pry

[1] pry(main)> def up_so_floating
[1] pry(main)*   puts "anyone lives in a pretty how town"
[1] pry(main)* end  
=> nil
[2] pry(main)> show-source up_so_floating

From: (pry) @ line 1:
Owner: Object
Visibility: private
Number of lines: 3

def up_so_floating
  puts "anyone lives in a pretty how town"
end
[3] pry(main)>

Example (recorded): superclass methods (with help of -s or --super flag).

[1] pry(main)> class Parent
[1] pry(main)*   def foo
[1] pry(main)*     :original
[1] pry(main)*   end  
[1] pry(main)* end  
=> nil
[2] pry(main)> class Child < Parent
[2] pry(main)*   def foo
[2] pry(main)*     :modified
[2] pry(main)*   end  
[2] pry(main)* end  
=> nil
[3] pry(main)> show-source Child#foo -s

From: (pry) @ line 2:
Owner: Parent
Visibility: public
Number of lines: 3

def foo
  :original
end
[4] pry(main)> show-source Child#foo

From: (pry) @ line 7:
Owner: Child
Visibility: public
Number of lines: 3

def foo
  :modified
end
[5] pry(main)> 

Advanced example (recorded):

[1] pry(main)> require 'delegate'
=> false
[2] pry(main)> show-source SimpleDelegator#__getobj__

From: /opt/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/delegate.rb @ line 264:
Owner: SimpleDelegator
Visibility: public
Number of lines: 3

def __getobj__
  @delegate_sd_obj
end
[3] pry(main)> show-source SimpleDelegator#__getobj__ --super

From: /opt/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/delegate.rb @ line 141:
Owner: Delegator
Visibility: public
Number of lines: 3

def __getobj__
  raise NotImplementedError, "need to define `__getobj__'"
end

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View the source code for Pry commands

In keeping with Pry's philosophy of making all source code accessible, even command source is viewable. Simply use show-source command_name.

Example (recorded):

[1] pry(main)> show-source gem-list

From: /home/curacao/.gem/ruby/1.9.3/gems/pry-0.9.11.4/lib/pry/commands/gem_list.rb 
Number of lines: 29

class Command::GemList < Pry::ClassCommand
  match 'gem-list'
  group 'Gems'
  description 'List and search installed gems.'

  banner <<-'BANNER'
    Usage: gem-list [REGEX]

    List all installed gems, when a regex is provided, limit the output to those
    that match the regex.
  BANNER

  def process(pattern = nil)
    pattern = Regexp.compile(pattern || '')
    gems    = Rubygem.list(pattern).group_by(&:name)

    gems.each do |gem, specs|
      specs.sort! do |a,b|
        Gem::Version.new(b.version) <=> Gem::Version.new(a.version)
      end

      versions = specs.each_with_index.map do |spec, index|
        index == 0 ? text.bright_green(spec.version.to_s) : text.green(spec.version.to_s)
      end

      output.puts "#{text.default gem} (#{versions.join ', '})"
    end
  end
end
[2] pry(main)>

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View source for Ruby Core (MRI C code)

When the pry-doc plugin is installed (gem install pry-doc) the C source for Ruby core methods (MRI) become available. As with pure Ruby methods, the show-source command is used to display the code.

Example (recorded):

[1] pry(main)> show-source Object#extend

From: eval.c (C Method):
Owner: Kernel
Visibility: public
Number of lines: 16

static VALUE
rb_obj_extend(int argc, VALUE *argv, VALUE obj)
{
    int i;

    if (argc == 0) {
    rb_raise(rb_eArgError, "wrong number of arguments (at least 1)");
    }
    for (i = 0; i < argc; i++)
    Check_Type(argv[i], T_MODULE);
    while (argc--) {
    rb_funcall(argv[argc], rb_intern("extend_object"), 1, obj);
    rb_funcall(argv[argc], rb_intern("extended"), 1, obj);
    }
    return obj;
}
[2] pry(main)>

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View Rubinius core source code

Rubinius is a great platform for Rubyists as nearly everything is implemented in pure Ruby. Pry takes advantage of this and the show-source command can display Rubinius core method source almost as easily as the source for standard methods.

Example (recorded):

[1] pry(main)> show-source Enumerable#group_by 

From: /opt/rubies/rubinius-2.0.0-rc1/kernel/common/enumerable.rb @ line 274:
Owner: Enumerable
Visibility: public
Number of lines: 15

def group_by
  return to_enum(:group_by) unless block_given?

  h = {}
  each do
    o = Rubinius.single_block_arg
    key = yield(o)
    if h.key?(key)
      h[key] << o
    else
      h[key] = [o]
    end
  end
  h
end

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View the source of the current method

When Pry is invoked at runtime from inside a method (using binding.pry) the source for the method can be viewed by typing simply show-source. No method name is required as the information on the current method is contained in the Binding object.

(recorded)

In the Ruby file:

def moon
  puts "If the gypsies come,"
  puts "they will use your heart"
  puts "to make white necklaces and rings."
  binding.pry
end

In the Pry session:

[1] pry(main)> show-source

From: /home/curacao/moon.rb @ line 1:
Owner: Object
Visibility: private
Number of lines: 6

def moon
  puts "If the gypsies come,"
  puts "they will use your heart"
  puts "to make white necklaces and rings."
  binding.pry
end
[2] pry(main)>

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View the source of the Lambdas and Procs

Pry can show source code of any Lambda or Proc object.

Example (recorded): defined inside Pry

[1] pry(main)> my_lambda = lambda { :hello_lambda! }
=> #<Proc:0x9f977e4@(pry):1 (lambda)>
[2] pry(main)> show-source my_lambda

From: (pry) 
Number of lines: 1

my_lambda = lambda { :hello_lambda! }
[3] pry(main)> my_proc = proc { :hello_proc! }
=> #<Proc:0xa7f3500@(pry):2>
[4] pry(main)> show-source my_proc

From: (pry) 
Number of lines: 1

my_proc = proc { :hello_proc! }
[5] pry(main)>

Example (recorded): defined in a file

[1] pry(main)> show-source Pry::DEFAULT_EXCEPTION_HANDLER

From: /home/curacao/.gem/ruby/1.9.3/gems/pry-0.9.11.4/lib/pry.rb 
Number of lines: 8

DEFAULT_EXCEPTION_HANDLER = proc do |output, exception, _|
  if UserError === exception && SyntaxError === exception
    output.puts "SyntaxError: #{exception.message.sub(/.*syntax error, */m, '')}"
  else
    output.puts "#{exception.class}: #{exception.message}"
    output.puts "from #{exception.backtrace.first}"
  end
end
[2] pry(main)>

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View the source of classes of arbitrary objects

It is possible to view a class definition of almost every Ruby object. The exception is empty classes. A class must define at least one method (either an instance method or a class method).

Example (recorded): objects whose classes are defined inside Pry

[1] pry(main)> class Hello
[1] pry(main)*   def world
[1] pry(main)*   end  
[1] pry(main)* end  
=> nil
[2] pry(main)> hello = Hello.new
=> #<Hello:0x9a2d27c>
[3] pry(main)> show-source hello

From: (pry) 
Number of lines: 4

class Hello
  def world
  end
end
[4] pry(main)>

Example (recorded): objects whose classes are defined in a file

[1] pry(main)> require 'tempfile'
=> false
[2] pry(main)> tf = Tempfile.new('hello')
=> #<File:/tmp/hello20130201-7601-1qyalim>
[3] pry(main)> show-source tf

From: /opt/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/tempfile.rb
Number of lines: 269

class Tempfile < DelegateClass(File)
  MAX_TRY = 10  # :nodoc:
  include Dir::Tmpname

  # call-seq:
  #    new(basename, [tmpdir = Dir.tmpdir], [options])
  #
  # Creates a temporary file with permissions 0600 (= only readable and
  # writable by the owner) and opens it with mode "w+".
:

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View the source of all definitions and monkey-patches of classes or modules

Note that Pry assumes a class is only monkey-patched at most once per file, so will not find multiple monkey-patches in the same file.

Example (recorded):

[1] pry(main)> edit a.rb
[2] pry(main)> edit b.rb
[3] pry(main)> show-source Foo

From: /home/curacao/a.rb 
Number of lines: 5

class Foo
  def one

  end
end
[4] pry(main)> show-source Foo -a
Found 2 candidates for `Foo` definition:

Candidate 1/2: /home/curacao/a.rb @ line 1:
Number of lines: 5

class Foo
  def one

  end
end

Candidate 2/2: /home/curacao/b.rb @ line 1:
Number of lines: 5

class Foo
  def two

  end
end
[5] pry(main)>

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