Can I make an array / multiple references in ruby on rails

Question

I'm working on a project and I need to be able to set one or more task to an event, for example in garden, there is a Client and we need to cut the grass and clean the pool, instead of creating 2 events I want to create one where the 2 tasks appears and be able to select both of them in the form.

Models

class Client < ...
 has_many :events

class Event
 belongs_to :user
 has_and_belongs_to_many :task
 belongs_to :client

class Task
 has_many :assigned_tasks

I was thinking that in the controller of the events, do something like this, but it didn't work, it says it can't map

def event_params
      params.require(:event).permit(:user_id, :client_id , task_ids:[])
    end

in the form I tryed using collection but it didnt work, I would like to do a drop down of checkboxes or dots, but I don't know hot to do it and by doing it all with checkboxes, it gave the same error as map, it couldn map nil class nil

form

<%=form.collection_check_boxes :task_id,@tasks, :id,:title %>
or
<%=form.collection_check_boxes :task_ids,@tasks, :id,:title %>

undefined method `map' for nil:NilClass

Answer 1

I found out how to solve it, In the controller I needed to change :task_id to , task_id:[] and in the form add

<%= form.collection_check_boxes :task_id, @tasks, :id, :title, multiple: true%>

multiple: true now the thing is That it can't show I made

event.task.each and gave me error, it says  PG::UndefineTable there is no relation <<events_tasks>>

But when i do

 events.task_id. each

it allows it but I can't show the title of the task now, please help