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README.markdown

Blobject is an experiment into using idosyncratic Ruby features to slop a Hash.

RDocs: http://sjltaylor.github.com/blobject

About

Consider the following json sample...

{
  "device_id": 63354,
  "channel_no": 6,
  "interval_ms": 15000,
  "readings": [
    {
      "value": 14232,
      "time": 1339880802
    },
    {
      "value": 14232,
      "time": 1339880817
    }
  ],
  "calibration": {
    "staff": {
      "name": {
        "first": "Carl",
        "middle_initial": "I",
        "second": "Brator"
      }
    },
    "last_calibration": "2010-06-16T22:06:42+01:00"
  }
}

Blobject lets you do this (complete code listing, no predefined data structures):

data = Blobject.from_json HTTParty.get('https://raw.github.com/sjltaylor/blobject/master/spec/sample_data/sample3.json')

full_name = "#{data.calibration.staff.name.first}#{data.calibration.staff.name.middle_initial}#{data.calibration.staff.name.second}".capitalize
  => "Calibrator"

last_reading = data.readings.last.value if data.readings?
  => 14232

Blobject is convenient for creating json payloads too. Blobjects are freeform which means you can do this...

data = Blobject.new

data.name   = "Johnny"
data.number = 316

like an OpenStruct, the members are not predefined attributes

unlike OpenStruct, Blobjects can be arbitrarily complex which means you can do this...

data = Blobject.new
  => {}

data.name.first   = "Johnny"
data.name.surname = "Begood"
  => {:name=>{:first=>"Johnny", :surname=>"Begood"}}

data.my.object.with.deep.nested.members = "happy place"
  => {:name=>{:first=>"Johnny", :surname=>"Begood"}, :my=>{:object=>{:with=>{:deep=>{:nested=>{:members=>"happy place"}}}}}}

You can assign hashes which become nested blobjects

data.details = { code: 41239, ref: "#22322" }

data.details.code => 41239 data.details.code = 11322 data.details.code => 11322 data.details.ref => "#22322"

You can test to see if a member is defined:

data.something_here?
  => false
data.name?
  => true

You can use it like a hash

data[:name]
  => {:first=>"Johnny", :surname=>"Begood"}

data[:name][:first] = "Jimmy"; data[:name]
  => {:first=>"Jimmy", :surname=>"Begood"}

data.empty?
  => false

data.name == {:first=>"Jimmy", :surname=>"Begood"}
  => true

You can get access to the internal hash with Blobject#hash or a de-blobjectified copy with Blobject#to_hash

You can call Blobject#freeze to prevent the data being modified. This still allows chained calls: blobject.data.nested.is_something_here? but assignments will raise RuntimeError: can't modify frozen Hash

You can work with JSON data using Blobject.from_json and Blobject#to_json, in Rails, you can use Blobject#as_json as you would with a hash.

You can work with YAML data using Blobject.from_yaml and Blobject#to_yaml.

Try it out...

  1. Install the gem (ruby 1.9.2+ required): sh <(curl https://raw.github.com/sjltaylor/blobject/master/try_blobject.sh)
  2. Load data from an api... payload = Blobject.from_json HTTParty.get('https://raw.github.com/sjltaylor/blobject/master/spec/sample_data/sample3.json')
  3. Inspect it payload.calibration.staff.name => {:first=>"Carl", :middle_initial=>"I", :second=>"Brator"}
  4. Test for optional data members payload.channel_no? => true payload.something_that_is_not_there? => false
  5. Draw your own payload mine = Blobject.new my: {data: 123} mine.to_json => "{"my":{"data":123}}"

Used for Configuration

Consider a configuration object which contains credentials for a third-party api.

third_party_api:
  secret_key: 'S3CR3T'
  endpoint: 'http://services.thirdparty.net/api'

With a hash, usage looks like this:

CONFIG[:third_party_api][:endpoint]

With a Blobject, usage looks like this:

CONFIG.third_party_api.endpoint

References to the endpoint are scattered throughout the codebase, then one day the endpoint is separated into its constituent parts to aide in testing and staging.

third_party_api:
  secret_key: 'S3CR3T'
  protocol: 'http'
  hostname: 'services.thirdparty.net'
  path: '/api'

Using a blobject we can easily avoid having to refactor our code...

CONFIG = Blobject.from_yaml(File.read('./config.yml'))

CONFIG.third_party_api.instance_eval do
  def endpoint
    "#{protocol}://#{hostname}#{path}"
  end
end

Serialization

Blobjects can be used to easily build complex payloads.

person = Blobject.new

person.name = first: 'David', last: 'Platt'

person.address.tap do |address|
  address.street = "..."
  address.city   = "..."
end

person.next_of_kin.address.city = '...'

# after the payload is constructed it can be frozen to prevent modification
person.freeze

A nice pattern in most cases is to use an initialization block...

Blobject.new optional_hash_of_initial_data do |b|
  b.name = ...
end.freeze

Suppose you receive a payload from an api which may or may not contain an address and city...

payload = Blobject.from_json request[:payload]

# if the payload does have an address...
city = payload.address.city
  => 'Liverpool'

# if the payload does not have an address or city
city = payload.address.city
  => nil
# rather than request[:payload][:address][:city] which would raise
# NoMethodError: undefined method `[]' for nil:NilClass

Also, you don't need to concern yourself whether hash keys are symbols or strings.

Performance

The runtime performance of something as low level as blobject deserves consideration.

see /benchmarks

ITERATIONS: 1000000


BENCHMARK: assign

            user       system     total       real
Object:     0.190000   0.000000   0.190000 (  0.229685)
Hash:       0.220000   0.000000   0.220000 (  0.230500)
OpenStruct: 0.520000   0.000000   0.520000 (  0.529861)
Blobject:   0.790000   0.000000   0.790000 (  0.808610)
Hashie:     8.270000   0.030000   8.300000 (  9.291184)


BENCHMARK: read

            user       system     total       real
Hash:       0.160000   0.000000   0.160000 (  0.165141)
Object:     0.170000   0.000000   0.170000 (  0.170228)
OpenStruct: 0.340000   0.000000   0.340000 (  0.342430)
Blobject:   0.410000   0.000000   0.410000 (  0.410574)
Hashie:     1.880000   0.000000   1.880000 (  1.921718)

Host CPU: 2.13GHz Core2

A Blobject is three-four times slower than an equivalent Object.

Limitations

  • will not work with basic objects unless #class and #freeze are implemented
  • cyclic blobject graphs result in infinite recursion causing a stack overflow
  • imho, blobject's behaviour leads to too many surprises and a simpler more explicit is better
  • Ruby 1.8.7 is not supported. Testing rubies...
    • mri 1.9.3-p194
    • mri 1.9.2-p290

Disclaimer

Blobject provides a convenient way to create large freeform data structures; With great power comes great blah blah blah blah...

License

(The MIT License)

Copyright © 2012 Sam Taylor

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ‘Software’), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ‘AS IS’, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Copyright (c) 2012 Sam Taylor. See LICENSE.txt for further details.

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