monkeypatch of wice_grid for draper support ( Inspired from https://github.com/leikind/wice_grid/issues/120 )

index.html.slim

== grid(@posts_grid) do |g|
  - g.column attribute: 'title'
  - g.column name: 'body' do |u|
    - u.truncated_body

post_decorator.rb

class PostDecorator < Draper::Decorator
  delegate_all

  def truncated_body
    object.body.truncate(15)
  end

end

posts_controller.rb

class PostsController < ApplicationController

  def index
    @posts_grid = initialize_grid Post, decorate: true
  end

end

wice_grid_draper_support_initializer.rb

if defined?(Wice::WiceGrid) && defined?(Draper::CollectionDecorator) && defined?(Draper::Decorator)

  module WiceGridDraperSupport
    def initialize(klass_or_relation, controller, opts = {})
      @decorate = opts.delete(:decorate)
      super
    end

    def read
      super
      @resultset = @resultset.decorate(klass: @klass) if @decorate == true
    end
  end

  module DraperCollectionWiceGridSupport
    active_record_methods = [
      :columns,
      :connection,
      :merge_conditions,
      :page,
      :table_name,
      :unscoped,
      :where
    ]
    delegate *active_record_methods, to: :klass

    active_record_relation_methods = [
      :current_page,
      :last_page?,
      :limit_value,
      :num_pages,
      :offset_value,
      :total_count,
      :total_pages
    ]

    delegate *active_record_relation_methods, to: :object

    attr_reader :klass

    def initialize(object, options = {})
      @klass = options.delete(:klass)
      super
    end

    def is_a?(klass)
      klass == ActiveRecord::Relation || super
    end
  end

  class Wice::WiceGrid
    prepend WiceGridDraperSupport
  end

  class Draper::CollectionDecorator
    prepend DraperCollectionWiceGridSupport
  end

  class Draper::Decorator
    def self.decorate_collection(object, options = {})
      options.assert_valid_keys(:with, :context, :klass)
      collection_decorator_class.new(object, options.reverse_merge(with: self))
    end
  end

end

I made a little tweak to allow the controller to specify which decorator to use.

  module WiceGridDraperSupport
    def initialize(klass_or_relation, controller, opts = {})
      @decorator = opts.delete(:decorator)
      super
    end

    def read
      super
       if @decorator < Draper::Decorator
         @resultset = @decorator.decorate_collection @resultset, klass: @klass
       elsif @decorator.present?
         @resultset = @resultset.decorate(klass: @klass)
       end
    end
  end