Rails Current Page Helper

path_helper.rb

module PathHelper
  
  ##
  # Checks whether you are on the specified page
  #
  # @param matchers A comma separated list of matchers.
  # @param returnval Return value if the page matches or nil. Defaults to true.
  # @return [mixed] returnval (usually truthy) on success or nil on failure.
  #
  # @example Check if you are on Article#show
  #   page?( 'article#show' )
  # @example Check if on Article#show or News#index
  #   page?( 'article#show, news#index' )
  # @example Check if you are in the article controller under the admin scope
  #   page?( 'admin/articles#index' )
  # @example Check if you are in the article controller and return `'active'`
  #   page?( 'article', 'active' )
  # @example Check aditional parameters and return `'active'` (for use as class)
  #   page?( "article#show?slug=#{@article.slug}", 'active' )
  #
  # ==== Matchers
  # Matchers are a comma separated list of rules specified with the following
  # format. Whitespace between matchers is allowed.
  #    controller#action?param1=value&param2=value
  # Values should be URL encoded if they contain special characters.
  #
  #
  # ==== LICENSE
  # Copyright (c) 2015-2017 Itay Grudev <itay[]grudev.com>
  # Published under the terms of The MIT License (MIT)
  #
  def page?( matchers, returnval = true )
    matchers.split( ',' ).each do |matcher|
      # Split the routing part and the parameters part
      routing, params = matcher.strip.split( '?' )
      # Split the controller from the action
      controller, action = routing.strip.split( '#' ) unless routing.blank?
      # Split multiple parameters
      params = params.strip.split( '&' ) unless params.blank?

      next if ! controller.blank? and request.params[:controller] != controller
      next if ! action.blank? and request.params[:action] != action

      # Verify parameters
      matches = true
      params.try( :each ) do |param|
        # Split parameter key from value
        key, value = param.strip.split( '=' )
        if request.params[key] != URI.unescape( value )
          matches = false and break
        end
      end
      next unless matches

      return returnval
    end

    nil
  end
 
end

~examples.slim

/ Checking if you are on a given page
- if page?( 'article#show' )
  / ...
- if page?( 'article#show, news#index' )
  / ...
 
/ Marking links as active
ul
  li class=[ page?( 'blog', 'active' ) ]
    = link_to 'Blog', blog_path
 
/ Usage with namespaces
ul
  li class=[ page?( 'admin/articles#index', 'active' ) ]
    = link_to 'Pages', admin_pages_path
 
/ Checking additional parameters
/ Assuming you have a path like: get '/article/:slug' => 'article#show'
ul
  - @pages.each do |page|
    li class=[ page?( "article#show?slug=#{@article.slug}", 'active' ) ]
      = link_to @page.title, page_path( @page.slug )

~path_helper_spec.rb

require 'rails_helper'

RSpec.describe PathHelper, type: :helper do

  describe 'page?' do
    before {
      @request = double( 'request' )
      allow( helper ).to receive( :request ).and_return( @request )
    }

    # This adds additional test with two matchers where the first is invalid
    [ '', 'INVALID#INVALID?invalid=invalid&invalid=invalid,' ].each do |prefix|
      context "with#{'out' if prefix.blank?} prefix" do
        context 'on matching page' do
          before {
            allow( @request ).to receive( :params ).and_return(
              controller: ( @controller = SecureRandom.hex ),
              action: ( @action = SecureRandom.hex )
            )
          }

          it 'matches just a controller' do
            expect(
              helper.page?( prefix + "#{@controller}" )
            ).to eq true
          end

          it 'matches just an action' do
            expect(
              helper.page?( prefix + "##{@action}" )
            ).to eq true
          end

          it 'matches just a controller and an action' do
            expect(
              helper.page?( prefix + "#{@controller}##{@action}" )
            ).to eq true
          end
        end

        context 'on controller mismatch' do
          before {
            allow( @request ).to receive( :params ).and_return(
              controller: '!' + ( @controller = SecureRandom.hex ),
              action: ( @action = SecureRandom.hex )
            )
          }

          it 'matches just a controller' do
            expect(
              helper.page?( prefix + "#{@controller}" )
            ).to be_nil
          end

          it 'matches just an action' do
            expect(
              helper.page?( prefix + "##{@action}" )
            ).to eq true
          end

          it 'matches just a controller and an action' do
            expect(
              helper.page?( prefix + "#{@controller}##{@action}" )
            ).to be_nil
          end
        end

        context 'on action mismatch' do
          before {
            allow( @request ).to receive( :params ).and_return(
              controller: ( @controller = SecureRandom.hex ),
              action: '!' + ( @action = SecureRandom.hex )
            )
          }

          it 'matches just a controller' do
            expect(
              helper.page?( prefix + "#{@controller}" )
            ).to eq true
          end

          it 'matches just an action' do
            expect(
              helper.page?( prefix + "##{@action}" )
            ).to be_nil
          end

          it 'matches just a controller and an action' do
            expect(
              helper.page?( prefix + "#{@controller}##{@action}" )
            ).to be_nil
          end
        end

        context 'with additional params specified' do
          it 'should return true on matching page' do
            allow( @request ).to receive( :params ).and_return(
              controller: ( @controller = SecureRandom.hex ),
              action: ( @action = SecureRandom.hex ),
              ( param1 = SecureRandom.hex ) => ( value1 = SecureRandom.hex ),
              ( param2 = SecureRandom.hex ) => ( value2 = SecureRandom.hex )
            )

            expect(
              helper.page?(
                "#{@controller}##{@action}?#{param1}=#{value1}&#{param2}=#{value2}"
              )
            ).to eq true
          end

          it 'should return nil if the page doesn\'t match' do
            allow( @request ).to receive( :params ).and_return(
              controller: ( @controller = SecureRandom.hex ),
              action: ( @action = SecureRandom.hex ),
              ( param1 = SecureRandom.hex ) => ( value1 = SecureRandom.hex ),
              ( param2 = SecureRandom.hex ) => ( value2 = SecureRandom.hex )
            )

            expect(
              helper.page?(
                "#{@controller}##{@action}?#{param1}=#{value1}&#{param2}=!#{value2}"
              )
            ).to be_nil
          end
        end

        context 'with return value specified' do
          it 'should return the specified value on matching page' do
            allow( @request ).to receive( :params ).and_return(
              controller: ( @controller = SecureRandom.hex ),
              action: ( @action = SecureRandom.hex )
            )

            expect(
              helper.page?(
                "#{@controller}##{@action}",
                ( val = SecureRandom.hex )
              )
            ).to eq val
          end

          it 'should return nil if the page doesn\'t match' do
            allow( @request ).to receive( :params ).and_return(
              controller: ( '!' + @controller = SecureRandom.hex ),
              action: ( '!' + @action = SecureRandom.hex )
            )

            expect(
              helper.page?(
                "#{@controller}##{@action}",
                ( val = SecureRandom.hex )
              )
            ).to be_nil
          end
        end
      end
    end
  end
end