ObjectInspector

ObjectInspector takes Object#inspect to the next level. Specify any combination of identification attributes, flags, issues, info, and/or a name along with an optional, self-definable scope option to represents objects. Great for the console, logging, etc.

Because object inspection code should be uniform, easy to build, and its output should be easy to read!

If you'd like to just jump into an example: Full Example.

Installation

Add this line to your application's Gemfile:

gem "object_inspector"

And then execute:

$ bundle

Or install it yourself:

$ gem install object_inspector

Compatibility

Tested MRI Ruby Versions:

• 2.3
• 2.4
• 2.5
• 2.6
• edge

ObjectInspector has no other dependencies.

Configuration

Global/default values for ObjectInspector can be configured via the ObjectInspector::Configuration object.

Note: In a Rails app, the following would go in e.g. config/initializers/object_inspector.rb

# Default values are shown.
ObjectInspector.configure do |config|
  config.formatter_class = ObjectInspector::TemplatingFormatter
  config.inspect_method_prefix = "inspect"
  config.default_scope = ObjectInspector::Scope.new(:self)
  config.wild_card_scope = "all"
  config.out_of_scope_placeholder = "*"
  config.presenter_inspect_flags = " ⇨ "
  config.name_separator = " - "
  config.flags_separator = " / "
  config.issues_separator = " | "
  config.info_separator = " | "
end

Usage

Given, an object of any type, call ObjectInspector::Inspector.inspect.

class MyObject
  def inspect
    ObjectInspector::Inspector.inspect(self)
  end
end

MyObject.new.inspect  # => "<MyObject>"

See also Helper Usage for an even simpler usage option.

Output Customization

Use the identification, flags, info, and/or name options to customize inspect output.

class MyObject
  def inspect
    ObjectInspector::Inspector.inspect(
      self,
      identification: "My Object",
      flags: "FLAG1 / FLAG2",
      info: "INFO",
      name: "NAME")
  end
end

MyObject.new.inspect  # => "<My Object(FLAG1 / FLAG2) INFO :: NAME>"

Or, define inspect_identification, inspect_flags, inspect_info, and/or inspect_name (or display_name) as either public or private methods on Object.

class MyObject
  def inspect
    ObjectInspector::Inspector.inspect(self)
  end

  private

  def inspect_identification; "My Object" end
  def inspect_flags; "FLAG1 / FLAG2" end
  def inspect_issues; "ISSUE1 | ISSUE2" end
  def inspect_info; "INFO" end
  def inspect_name; "NAME" end  # Or: def display_name; "NAME" end
end

MyObject.new.inspect
# => "<My Object(FLAG1 / FLAG2) !!ISSUE1 | ISSUE2!! INFO :: NAME>"

Helper Usage

To save some typing, include ObjectInspector::InspectHelper into an object and ObjectInspector::Inspector.inspect will be called on self automatically.

class MyObject
  include ObjectInspector::InspectorsHelper
end

MyObject.new.inspect  # => "<MyObject>"

To access the ObjectInspector::Inspector's options via the helper, call into super.

class MyObject
  include ObjectInspector::InspectorsHelper

  def inspect
    super(identification: "My Object",
          flags: "FLAG1",
          issues: "ISSUE1 | ISSUE2",
          info: "INFO",
          name: "NAME")
  end
end

MyObject.new.inspect
# => "<My Object(FLAG1) !!ISSUE1 | ISSUE2!! INFO :: NAME>"

Or, define inspect_identification, inspect_flags, inspect_info, and/or inspect_name (or display_name) in Object.

class MyObject
  include ObjectInspector::InspectorsHelper

  private

  def inspect_identification; "My Object" end
  def inspect_flags; "FLAG1 / FLAG2" end
  def inspect_issues; "ISSUE1 | ISSUE2" end
  def inspect_info; "INFO" end
  def inspect_name; "NAME" end  # Or: def display_name; "NAME" end
end

MyObject.new.inspect
# => "<My Object(FLAG1) !!ISSUE1 | ISSUE2!! INFO :: NAME>"

Scopes

Use the scope option to define the scope of the inspect_* methods. The supplied value will be wrapped by the ObjectInspector::Scope helper object. The default value is ObjectInspector::Scope.new(:self).

Scope Names

ObjectInspector::Scope acts like ActiveSupport::StringInquirer. This is a prettier way to test for a given type of "scope" within objects.

The ObjectInspector::Scope objects in these examples are the same as specifying <scope_name> like this:

my_object.inspect(scope: <scope_name>)

Options:

• :self (Default) -- Is meant to confine object interrogation to self (don't interrogate neighboring objects).
• :all -- Is meant to match on all scopes, regardless of their name.
• <custom> -- Anything else that makes sense for the object to key on.

scope = ObjectInspector::Scope.new
scope.self?     # => true
scope.verbose?  # => false
scope.complex?  # => false

Multiple Scope Names

It is also possible to pass in multiple scope names to match on.

scope = ObjectInspector::Scope.new(i[verbose complex])
scope.self?     # => false
scope.verbose?  # => true
scope.complex?  # => true

The "Wild Card" Scope

Finally, :all is a "wild card" scope name, and will match on all scope names.

scope = ObjectInspector::Scope.new(:all)
scope.self?     # => true
scope.verbose?  # => true
scope.complex?  # => true

Scope blocks

Passing a block to a scope predicate falls back to the out-of-scope placeholder (* by default) if the scope does not match.

scope = ObjectInspector::Scope.new(:verbose)
scope.verbose? { "MATCH" }  # => "MATCH"
scope.complex? { "MATCH" }  # => "*"

Scope Joiners

ObjectInspector::Scope also offers helper methods for uniformly joining inspect elements:

• join_name -- Joins name parts with - by default
• join_flags -- Joins flags with / by default
• join_info -- Joins info items with | by default

scope = ObjectInspector::Scope.new(:verbose)
scope.join_name([1, 2, 3])  # => "1 - 2 - 3"
scope.join_name([1, 2, 3, nil])  # => "1 - 2 - 3"
scope.join_flags([1, 2, 3])  # => "1 / 2 / 3"
scope.join_flags([1, 2, 3, nil])  # => "1 / 2 / 3"
scope.join_info([1, 2, 3])   # => "1 | 2 | 3"
scope.join_info([1, 2, 3, nil])   # => "1 | 2 | 3"

Full Example

class MyObject
  include ObjectInspector::InspectorsHelper

  attr_reader :name,
              :a2

  def initialize(name, a2 = 2)
    @name = name
    @a2 = a2
  end

  def associated_object1
    OpenStruct.new(flags: "AO1_FLAG1")
  end

  def associated_object2
    OpenStruct.new(flags: "AO2_FLAG1")
  end

  # Or `def inspect_name`
  def display_name(scope:)
    name
  end

  private

  def inspect_identification
    identify(:a2)
  end

  def inspect_flags(scope:)
    flags = ["DEFAULT_FLAG"]

    flags <<
      scope.verbose? {
        [
          associated_object1.flags,
          associated_object2.flags,
        ]
      }

    scope.join_flags(flags)
  end

  def inspect_issues
    "!!WARNING!!"
  end

  def inspect_info(scope:)
    info = ["Default Info"]
    info << "Complex Info" if scope.complex?
    info << scope.verbose? { "Verbose Info" }

    scope.join_info(info)
  end
end

my_object = MyObject.new("Name")

my_object.inspect(scope: :complex)
# => "<MyObject[a2:2](DEFAULT_FLAG / *) !!!!WARNING!!!! Default Info | Complex Info | * :: Name>"

my_object.inspect(scope: :verbose)
# => "<MyObject[a2:2](DEFAULT_FLAG / AO1_FLAG1 / AO2_FLAG1) !!!!WARNING!!!! Default Info | Verbose Info :: Name>"

my_object.inspect(scope: i[self complex verbose])
# => "<MyObject[a2:2](DEFAULT_FLAG / AO1_FLAG1 / AO2_FLAG1) !!!!WARNING!!!! Default Info | Complex Info | Verbose Info :: Name>"

my_object.inspect(scope: :all)
# => "<MyObject[a2:2](DEFAULT_FLAG / AO1_FLAG1 / AO2_FLAG1) !!!!WARNING!!!! Default Info | Complex Info | Verbose Info :: Name>"

my_object.inspect
# => "<MyObject[a2:2](DEFAULT_FLAG / *) !!!!WARNING!!!! Default Info | * :: Name>"

ObjectInspector.configuration.default_scope = :complex
my_object.inspect
# => "<MyObject[a2:2](DEFAULT_FLAG / *) !!!!WARNING!!!! Default Info | Complex Info | * :: Name>"

ObjectInspector.configuration.default_scope = i[self complex verbose]
my_object.inspect
# => "<MyObject[a2:2](DEFAULT_FLAG / AO1_FLAG1 / AO2_FLAG1) !!!!WARNING!!!! Default Info | Complex Info | Verbose Info :: Name>"

ObjectInspector.configuration.default_scope = :all
my_object.inspect
# => "<MyObject[a2:2](DEFAULT_FLAG / AO1_FLAG1 / AO2_FLAG1) !!!!WARNING!!!! Default Info | Complex Info | Verbose Info :: Name>"

Wrapped Objects

If the Object being inspected wraps another object -- i.e. defines #to_model and #to_model returns an object other than self -- the inspect output will re-inspect the wrapped object. The wrapper points to the wrapped object with an arrow (⇨).

class MyWrapperObject
  include ObjectInspector::InspectorsHelper

  def to_model
    @to_model ||= MyWrappedObject.new
  end

  private

  def inspect_flags; "WRAPPER_FLAG1" end
end

class MyWrappedObject
  include ObjectInspector::InspectorsHelper

  private

  def inspect_flags; "FLAG1 / FLAG2" end
  def inspect_info; "INFO" end
end

MyWrapperObject.new.inspect
# => "<MyWrapperObject(WRAPPER_FLAG1)> ⇨ <MyWrappedObject(FLAG1 / FLAG2) INFO>"

This feature is recursive.

Wrapped Delegators

If the Object being inspected is wrapped by an object that delegates all unknown methods to the wrapped object, then inspect flags will be doubled up. To get around this, redefine the inspect method in the Wrapper object e.g. like:

class MyDelegatingWrapperObject
  include ObjectInspector::InspectorsHelper

  def initialize(my_object)
    @my_object = my_object
  end

  def inspect(**kargs)
    super(identification: self.class.name,
          name: nil,
          flags: nil,
          info: nil,
          issues: nil,
          **kargs)
  end

  def to_model
    @my_object
  end

  private

  def method_missing(method_symbol, *args)
    @my_object.__send__(method_symbol, *args)
  end

  def respond_to_missing?(*args)
    @my_object.respond_to?(*args) || super
  end
end

class MyWrappedObject
  include ObjectInspector::InspectorsHelper

  def display_name
    "WRAPPED_OBJECT_NAME"
  end

  private

  def inspect_flags; "FLAG1" end
  def inspect_info; "INFO" end
  def inspect_issues; "ISSUE1" end
  def inspect_name; "NAME" end
end

MyDelegatingWrapperObject.new(MyWrappedObject.new).inspect
# => "<MyDelegatingWrapperObject>  ⇨  <MyWrappedObject(FLAG1) !!ISSUE1!! INFO :: NAME>"

On-the-fly Inspect Methods

When passed as an option (as opposed to being called via an Object-defined method) symbols will be called/evaluated on Object on the fly.

class MyObject
  include ObjectInspector::InspectorsHelper

  def my_method1; "Result1" end
  def my_method2; "Result2" end

  def inspect_info; :my_method2 end
end

MyObject.new.inspect(info: "my_method1")  # => "<MyObject my_method1>"
MyObject.new.inspect(info: :my_method2)   # => "<MyObject Result2>"
MyObject.new.inspect                      # => "<MyObject my_method2>"

Clearing Output for Specified Inspect Method

Pass nil to any inspect method type to not display it:

class MyObject
  include ObjectInspector::InspectorsHelper

  def inspect_identification; "My Object" end
  def inspect_info; "INFO" end
  def inspect_flags; "FLAG1" end
  def inspect_issues; "ISSUE1" end
end

MyObject.new.inspect
# => "<My Object(FLAG1) !!ISSUE1!! INFO>"
MyObject.new.inspect(info: nil, flags: nil, issues: nil)
# => "<My Object>"
MyObject.new.inspect(identification: nil, info: nil, flags: nil, issues: nil)
# => "<MyObject>"

Custom Formatters

A custom inspect formatter can be defined by implementing the interface defined by ObjectInspector::BaseFormatter. Then, either override the ObjectInspector::Configuration#formatter_class value (see Configuration) or just pass your custom class name into ObjectInspector::Inspector.new.

class MyCustomFormatter < ObjectInspector::BaseFormatter
  def call
    "[#{identification} Flags: #{flags} -- Info: #{info} -- Name: #{name}]"
  end
end

class MyObject
  include ObjectInspector::InspectorsHelper

  def inspect
    super(formatter: MyCustomFormatter,
          identification: "IDENTIFICATION",
          flags: "FLAG1 / FLAG2",
          info: "INFO",
          name: "NAME")
  end
end

MyObject.new.inspect
# => "[IDENTIFICATION Flags: FLAG1 / FLAG2 -- Info: INFO -- Name: NAME]"

See examples:

• ObjectInspector::TemplatingFormatter
• ObjectInspector::CombiningFormatter

Supporting Gems

ObjectInspector works great with the ObjectIdentifier gem.

class MyObject
  include ObjectInspector::InspectorsHelper

  def my_method1
    1
  end

  def my_method2
    2
  end

  private

  def inspect_identification
    identify(:my_method1, :my_method2)
  end

  def inspect_flags; "FLAG1 / FLAG2" end
  def inspect_issues; "ISSUE1 | ISSUE2" end
  def inspect_info; "INFO" end
  def inspect_name; "NAME" end
end

MyObject.new.inspect
# => "<MyObject[my_method1:1, my_method2:2](FLAG1 / FLAG2) !!ISSUE1 | ISSUE2!! INFO :: NAME>"

Performance

Benchmarking ObjectInspector

ObjectInspetor is ~4x slower than Ruby's default inspect.

Performance of ObjectInspect can be tested by playing the ObjectInspector Benchmarking Scripts in the pry console for this gem.

play scripts/benchmarking/object_inspector.rb
# Comparison:
#                 Ruby:    30382.2 i/s
# ObjectInspector::Inspector:     7712.2 i/s - 3.94x  slower

Benchmarking Formatters

ObjectInspector::TemplatingFormatter -- which is the default Formatter -- outperforms ObjectInspector::CombiningFormatter by about 30% on average.

Performance of Formatters can be tested by playing the Formatters Benchmarking Scripts in the pry console for this gem.

play scripts/benchmarking/formatters.rb
# == Averaged =============================================================
# ...
#
# Comparison:
# ObjectInspector::TemplatingFormatter:    45725.3 i/s
# ObjectInspector::CombiningFormatter:    34973.9 i/s - 1.31x  slower
#
# == Done

Benchmarking Custom Formatters

Custom Formatters may be similarly gauged for comparison by adding them to the custom_formatter_klasses array before playing the script.

custom_formatter_klasses = [MyCustomFormatter]

play scripts/benchmarking/formatters.rb
# == Averaged =============================================================
# ...
#
# Comparison:
#    MyCustomFormatter:    52001.2 i/s
# ObjectInspector::TemplatingFormatter:    49854.2 i/s - same-ish: difference falls within error
# ObjectInspector::CombiningFormatter:    38963.5 i/s - 1.33x  slower
#
# == Done

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/pdobb/object_inspector.

License

The gem is available as open source under the terms of the MIT License.