如何在控制器中设置变量集，在其他类中可用？

Question

In my controller I have:

  def index
    @grid = UsersGrid.new(params[:users_grid]) do |scope|
      scope.where(admin: false).page(params[:page]).per_page(30)
    end
    @grid.assets
    if (current_user && current_users.admin?)
      @show_column = true
    else
      @show_column = false
    end
  end

In my grid class:

class UsersGrid

  include Datagrid
  scope do
    User.order("users.created_at desc")
  end

  column(:abc, :header => "abc?", :html => true, :if => proc {@show_column == true}) do |user|
    image_tag("abc.png", title: "abc") if user.abc
  end
end

So in the controller I set @show_column , and in the class it should show the column :abc depending on whether @show_column is true or false. This goes wrong as @show_column is an instance variable and not available in the grid class. So it's nil. How should I change this to make this work?

Answer 1

You can pass down the variable when creating the UsersGrid instance, then save it in an instance variable there.

In controller:

def index
  @show_column = (current_user && current_users.admin?)
  @grid = UsersGrid.new(params[:users_grid], @show_column) do |scope|
    scope.where(admin: false).page(params[:page]).per_page(30)
  end
  @grid.assets
end

In the grid class:

class UsersGrid
  def initialize(*params, show_column)
    super *params
    @show_column = show_column
  end

  # ...
end

Answer 2

You can use attr_accessor for a variable that is not a column of a table.

def index
    params[:users_grid][:show_column] = (current_user && current_users.admin?)
    @grid = UsersGrid.new(params[:users_grid]) do |scope|
      scope.where(admin: false).page(params[:page]).per_page(30)
    end
    @grid.assets    
  end

class UsersGrid

  include Datagrid
  scope do
    User.order("users.created_at desc")
  end
attr_accessor :show_column

  column(:abc, :header => "abc?", :html => true, :if => proc {self.show_column == true}) do |user|
    image_tag("abc.png", title: "abc") if user.abc
  end
end