# DeepPluck
[](http://rubygems.org/gems/deep_pluck)
[](https://travis-ci.org/khiav223577/deep_pluck)
[](http://rubygems.org/gems/deep_pluck)
[](https://codeclimate.com/github/khiav223577/deep_pluck)
[](https://codeclimate.com/github/khiav223577/deep_pluck/coverage)
Allow you to pluck deeply into nested associations without loading a bunch of records.
Support Rails 3.2, 4.2, 5.0, 5.1, 5.2, 6.0.
## Installation
Add this line to your application's Gemfile:
```ruby
gem 'deep_pluck'
```
And then execute:
$ bundle
Or install it yourself as:
$ gem install deep_pluck
## Usage
### Similar to #pluck method
```rb
User.deep_pluck(:id, :name)
# SELECT `users`.`id`, `users`.`name` FROM `users`
# =>
# [
# {'id' => 1, 'name' => 'David'},
# {'id' => 2, 'name' => 'Jeremy'},
# ]
```
### Pluck attributes from nested associations
```rb
User.deep_pluck(:name, 'posts' => :title)
# SELECT `users`.`id`, `users`.`name` FROM `users`
# SELECT `posts`.`user_id`, `posts`.`title` FROM `posts` WHERE `posts`.`user_id` IN (1, 2)
# =>
# [
# {
# 'name' => 'David' ,
# 'posts' => [
# {'title' => 'post1'},
# {'title' => 'post2'},
# ],
# },
# {
# 'name' => 'Jeremy',
# 'posts' => [
# {'title' => 'post3'},
# ],
# },
# ]
```
### Pluck at models
```rb
user = User.find_by(name: 'David')
user.deep_pluck(:name, :posts => :title)
# =>
# {
# 'name' => 'David' ,
# :posts => [
# {'title' => 'post1'},
# {'title' => 'post2'},
# ],
# }
```
### Compare with using `#as_json`
Assume the following relations:
> User has_many Posts.
> Post has_many PostComments.
> User has_one Contact.
And the following #as_json example:
```rb
User.where(:name => %w(Pearl Kathenrie)).includes([{:posts => :post_comments}, :contact]).as_json({
:root => false,
:only => [:name, :email],
:include => {
'posts' => {
:only => :name,
:include => {
'post_comments' => {
:only => :comment,
},
},
},
'contact' => {
:only => :address,
},
},
})
```
It works as expected, but is not very DRY, repeat writing `include`, `posts`, `post_comments` so many times.
Not to mention the huge performace improvement by using #deep_pluck.
You could refactor the example with #deep_pluck:
```rb
User.where(:name => %w(Pearl Kathenrie)).deep_pluck(
:name,
:email,
'posts' => [:name, 'post_comments' => :comment],
'contact' => :address,
)
```
### Better Performance
#deep_pluck return raw hash data without loading a bunch of records, so that faster than #as_json, or #select.
The following is the benchmark test on 3 users, 6 posts, where `users` table have 14 columns and `posts` have 6 columns. As it shows, `deep_pluck` is 4x faster than `as_json`.
```rb
# Repeat 500 times
# User.includes(:posts).as_json(:only => :email, :include => {:posts => {:only => :title}})
# User.deep_pluck(:email, {'posts' => :title})
user system total real
as_json 1.740000 1.230000 2.970000 ( 3.231465)
deep_pluck 0.660000 0.030000 0.690000 ( 0.880018)
```
The following is the benchmark test on 10000 users, where `users` table have 46 columns. As it shows, `deep_pluck` is 40x faster than `as_json` and 4x faster than `map`.
```rb
# Repeat 1 times
# User.select('account, email').map{|s| {'account' => s.account, 'email' => s.email}}
# User.select('account, email').as_json(:only => [:account, :email])
# User.deep_pluck(:account, :email)
user system total real
map 0.210000 0.000000 0.210000 ( 0.225421)
as_json 1.980000 0.060000 2.040000 ( 2.042205)
deep_pluck 0.040000 0.000000 0.040000 ( 0.051673)
```
## 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](https://rubygems.org).
## Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/khiav223577/deep_pluck. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
## License
The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).