SortParam

Sort records using a query parameter based on JSON API's sort parameter format.

In a nutshell, this gem converts comma-separated sort fields from this:

?sort=+users.first_name,-users.last_name:nulls_last,users.email

to this:

users.first_name asc, users.last_name desc nulls last, users.email asc

or to this:

{"users.first_name"=>{:direction=>:asc}, "users.last_name"=>{:direction=>:desc, :nulls=>:last}, "users.email"=>{:direction=>:asc}}

Features

• Sort field whitelisting.
• Supports ORDER BY expression generation for MySQL and PG.
• Parsing of comma-separated sort fields into hash for any further processing.
• Specifying NULL sort order.

Installation

Add this line to your application's Gemfile:

gem 'sort_param'

And then execute:

bundle install

Or install it yourself as:

gem install sort_param

Usage

Basic

1. Whitelist/define the sort fields

sort_param = SortParam.define do
               field :first_name, nulls: :first
               field :last_name
             end

This is is equivalent to:

sort_param = SortParam::Definition.new
                                  .field(:first_name, nulls: :first)
                                  .field(:last_name)

field method accepts the column name as the first argument. Any default column configuration such as :nulls(for NULLS FIRST or NULLS LAST sort order) follows the name.

2. Parse sort fields from a parameter

The load! method translates a given sort string/fields parameter to an SQL ORDER BY expression or to a Hash:

I. PostgreSQL example

sort_param.load!("+first_name,-last_name", mode: :pg)

=> "first_name asc nulls first, last_name desc"

II. MySQL example

sort_param.load!("+first_name,-last_name", mode: :mysql)

=> "first_name is not null, first_name asc, last_name desc"

III. Hash example

sort_param.load!("+first_name,-last_name")

=> {"first_name"=>{:nulls=>:first, :direction=>:asc}, "last_name"=>{:direction=>:desc}}

Any other additional column option set in SortParam::Definition or SortParam.define will be included in the column's hash value. For example:

sort_param = SortParam.define do
               field :first_name, foo: :bar, nulls: :first
             end

sort_param.load!("+first_name")
=> {"first_name"=>{:foo=>:bar, :nulls=>:first, :direction=>:asc}}

sort_param.load!("-first_name:nulls_last")
=> {"first_name"=>{:foo=>:bar, :nulls=>:last, :direction=>:desc}}

IV. Example with explicit nulls sort order

Example in PG mode:

sort_param.load!("+first_name:nulls_last,-last_name:nulls_first", mode: :pg)

=> "first_name asc nulls last, last_name desc nulls first"

Ignoring non-whitelisted sort fields instead of raising error

Use #load method instead:

  sort_param = SortParam.define do
                 field :first_name
               end

  sort_param.load("+first_name,+last_name", mode: :pg)
  => "first_name asc"

Output a different field name

Set the :rename field option to a string value or a Proc to output a different field name.

  sort_param = SortParam.define do
                 field :first_name, rename: 'users.name'
                 field :last_name, rename: ->(col) { "users.#{col}" }
               end
  
  sort_param.load!("+first_name", mode: :pg)
  => "users.name asc"
  
  sort_param.load!("+first_name", mode: :mysql)
  => "users.name asc"
  
  sort_param.load!("+first_name")
  => {"users.name"=>{:direction=>:asc}}

  sort_param.load!("+last_name")
  => {"users.last_name"=>{:direction=>:asc}}

Whitelisting multiple fields with the same options at once

Use #fields instead of #field:

  SortParam.define do
    fields :first_name, :last_name, nulls: :first, rename: ->(col) { "users.#{col}" }
    field :email
  end

NOTE: Unlike #field, #fields can only accept a Proc for the :rename option.

Rails example

controller

def index 
  render json: User.all.order(sort_fields)
end

private

def sort_fields
  SortParam.define do
    field :first_name
    field :last_name, nulls: :first
  end.load!(sort_param, mode: :pg)
end

# Fetch the sort fields from :sort query parameter.
# If none is given, default sort by `first_name ASC` and `last_name ASC NULLS FIRST`.
def sort_param
  params[:sort].presence || "+first_name,+last_name"
end

We can DRY this up a bit by creating a concern:

controllers/concerns/has_sort_param.rb

module HasSortParam
  extend ActiveSupport::Concern

  def sort_param(default: nil, &block)
    raise ArgumentError.new('Missing block') unless block_given?

    definition = SortParam.define(&block)
    definition.load!(params[:sort].presence || default, mode: :pg)
  end
end

controller v2

def index 
  render json: User.all.order(sort_fields)
end

private

def sort_fields
  sort_param default: '+first_name,-last_name' do
    field :first_name
    field :last_name, nulls: :first
  end
end

Error

Class	Description
SortParam::UnsupportedSortField	Raised when loading sort string via #load! and a sort field from the parameter isn't included in the whitelisted sort fields.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/jsonb-uy/sort_param.

License

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