Object Identifier

Object Identifier allows quick, easy, and uniform identification of an object by inspecting its class name and outputting any desirable attributes/methods. It is great for logging, sending descriptive notification messages, etc.

For example:

some_object.identify(:id, :name)

Which is the same as:

"#{some_object.class.name}[id:#{some_object.id}, name:\"#{some_object.name}\"]"

Installation

Add this line to your application's Gemfile:

gem "object_identifier"

And then execute:

$ bundle

Or install it yourself as:

$ gem install object_identifier

Compatibility

Tested MRI Ruby Versions:

• 3.2.0
• 2.4.9
• 2.5.8
• 2.6.6

Configuration

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

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

# Default values are shown.
ObjectIdentifier.configure do |config|
  config.formatter_class = ObjectIdentifier::StringFormatter
  config.default_attributes = i[id]
end

Usage

Defaults

identify outputs the id of the receiving object by default, if it exists and no other attributes/methods are specified.

my_movie.identify                # => Movie[1]

identify doesn't output labels if only identifying a single attribute/method. It includes labels when two or more attributes/methods are being identified.

my_movie.identify(:id)           # => Movie[1]
my_movie.identify(:rating)       # => Movie["7/10"]
my_movie.identify(:id, :rating)  # => Movie[id:1, rating:"7/10"]

Private methods can be identified just the same as public methods.

my_movie.identify(:my_private_method)  # => Movie["Shh"]

Unknown Attributes/Methods

If the object doesn't respond to a specified attribute/method it is simply ignored:

my_movie.identify(:id, :rating, :other)  # => Movie[id:1, rating:"7/10"]

Overriding Class Names

my_delayed_job.identify(klass: "Delayed::Job")  # => Delayed::Job[1]
my_movie.identify(klass: nil)                   # => [1]

Identifying Nil

nil.identify(:id, :name)                 # => [no objects]
nil.identify(:id, :name, klass: "Nope")  # => [no objects]

Collections

Collections of objects are each identified in turn.

[my_movie, my_user].identify(:id, :name)
# => Movie[id:1, name:"Pi"], User[id:1, name:"Bob"]

The number of results that will be identified from a collection can be truncated by specifying the limit option.

[my_movie, my_user].identify(:id, :name, limit: 1)
# => Movie[id:1, name:"Pi"], ... (1 more)

Empty Collections

[].identify  # => [no objects]
{}.identify  # => [no objects]

Custom Object Identifiers

Internally, Object Identifier calls inspect_lit to return a "literally-inspected" string representation of an object. This works because Object, itself, is monkey-patched to define inspect_lit which just returns inspect. This is sufficient for most objects, but some objects will benefit from defining special output from inspect_lit.

Object Identifier defines inspect_lit on three other core objects: String, Symbol, and BigDecimal.

"a_string".inspect_lit           # => "\"a_string\""
:a_symbol.inspect_lit            # => ":\"a_symbol\""
BigDecimal(1.99, 3).inspect_lit  # => "<BD:1.99>"

To identify an object in a special way, just define inspect_lit to return a custom String.

class MyValueObject
  def initialize(val)
    @val = val
  end

  def inspect_lit
    "#{@val} Meters"
  end
end

my_value_object = MyValueObject.new(42)
OpenStruct.new(my_value: my_value_object).identify(:my_value)
# => "OpenStruct[my_value:42 Meters]"

Supporting Gems

ObjectIdentifier works great with the ObjectInspector gem.

Benchmarking Formatters

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

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
# ObjectIdentifier::StringFormatter
#     58.478k (± 0.8%) i/s -    295.776k in   5.058178s
# MyCustomFormatter
#                          ...

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_identifier.

License

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