How to handle multiple conditions of instance variable assignment

Question

I have the following in my controller that will assign a different collection of results depending on what params are received with an Ajax call. It is messy and i would like to just call a function with all the logic in rather than all this in my index controller

class PublicController < ApplicationController
  def index
    if params[:literacy_param].present?
      @skills = Skill.search(params)
    elsif params[:numeracy_param].present?
      @skills = Skill.numeracy_default_params
    elsif params[:numeracy_number_skills].present?
      @skills = Skill.numeracy_number_skills
    elsif params[:numeracy_measuring_skills].present?
      @skills = Skill.numeracy_measuring_skills
    elsif params[:numeracy_data_skills].present?
      @skills = Skill.numeracy_data_skills
    else
      @skills = Skill.default_params
    end
  end
end

Im just a bit unsure on how to set out my function so that it can read the params that are being sent,

I have come up with this so far

private
 def skills(params)
   if params[:literacy_param].present?
     @skills = Skill.search(params)
   elsif params[:numeracy_param].present?
     @skills = Skill.numeracy_default_params
   elsif params[:numeracy_number_skills].present?
    @skills = Skill.numeracy_number_skills
   elsif params[:numeracy_measuring_skills].present?
    @skills = Skill.numeracy_measuring_skills
   elsif params[:numeracy_data_skills].present?
    @skills = Skill.numeracy_data_skills
   else
    @skills = Skill.default_params
   end    
 end

Then in my index action i would do

@skills = skills(params)

would this be an efficient way?

Thanks

just info. you can also do @skills = if condition ... end instead of repeating @skills all over. being DRY ;) — Nithin
– Nithin, Commented Jan 5, 2015 at 9:14

Rajdeep Singh · Accepted Answer · 2015-01-05 09:35:22Z

3

You can do this

class PublicController < ApplicationController
  def index
    skills = ['literacy_param', 'numeracy_param', 'numeracy_number_skills', 'numeracy_measuring_skills', 'numeracy_data_skills']
    common_in_params = (skills & params).first
    @skills = common_in_params.present? ? (common_in_params.eql?('literacy_param') ? Skill.search(params) : Skill.send(common_in_params)) : Skill.default_params                
  end
end

You can define skills array in an initializer for resusability

edited Jan 5, 2015 at 9:35

answered Jan 5, 2015 at 9:26

Rajdeep Singh

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1 Comment

BroiSatse Over a year ago

There is a small difference to the original implementation - if literacy_params is an empty string it will use the default. I would go with common_in_params = skills.find {|skill| params[skill].present?} to fix it.

oldhomemovie · Accepted Answer · 2015-01-05 09:31:14Z

1

One way of doing it would be this:

def skills(params)
  set_of_skills = params.slice(
    :numeracy_param,
    :numeracy_number_skills,
    :numeracy_measuring_skills,
    :numeracy_data_skills,
  ).first

  @skills = if params[:literacy_param]
    Skill.search(params)
  elsif set_of_skills
    Skill.public_send(set_of_skills)
  else
    Skill.default_params
  end
end

I would also advise to have this extracted into a lib/ folder, and unit-tested. So that in your controller you could perform the following:

def index
  @skills = SkillSearch.new(params).search
end

answered Jan 5, 2015 at 9:31

oldhomemovie

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Comments

Surya · Accepted Answer · 2015-01-05 10:28:19Z

Two ways I can think of doing this right now:

Wrap the params in a unique key. As in params = { :keyword => :literacy_param }, and then use this unique key to identify the right operation.

In you skill.rb:

def self.filter(params)
  if params[:keyword] == :literacy_param
    search(params)
  elsif available_filters.include?(params[:keyword])
    public_send(params[:keyword])
  else
    default_params
  end
end

private

  def self.available_filters
    %i{numeracy_default_params numeracy_number_skills numeracy_measuring_skills numeracy_data_skills}
  end

considering that instead of :numeracy_param, you send :numeracy_default_params in :keyword key. Otherwise you'll have to make another elsif inside filter method.

then in your index method:

def index
  @skilles = Skill.filter(params)
end

You create a separate filter class, which is an expandable solution, just in case when you need to go for complex search queries and filtering.

Let's call it SkillSeacrher, inside you app/models/skill_searcher.rb:

class SkillSearcher
  attr_reader :keyword

  def initialize(keyword)
    @keyword = keyword
  end

  def filter
    if keyword == :literacy_param
      Skill.search(params)
    elsif available_filters.include?(keyword)
      Skill.public_send(keyword)
    else
      Skill.default_params
    end
  end

  private

    def self.available_filters
      %i{numeracy_default_params numeracy_number_skills numeracy_measuring_skills numeracy_data_skills}
    end
end

then in index method:

def index
  @skills = SkillSearcher.new(params[:keyword]).filter
end

However, you can do one more change to filter method(depends on your taste):

def filter
  if keyword == :literacy_param
    Skill.search(params)
  else
    Skill.public_send(available_filters.include?(keyword) ? keyword : :default_params)
  end
end

And, if you have all these methods accepting params as arguments then it'd be much more sleek:

def filter
  Skill.public_send(available_filters.include?(keyword) ? keyword : :default_params, params)
end

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