Undefined method 'each' for nil class in create method - ruby-on-rails

Question

I'm getting an undefined method 'each' for nil class in my create method for a join table that I have.
I've got one join table for Emotions_pins and one for casues_pins the emotions pins table works fine but I'm getting the error on causes. Here's the code
_form.html.erb for Pin
<%= form_for(#pin) do |f| %>
<%= f.hidden_field :user_id, :value => current_user.id %>
<% if #pin.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#pin.errors.count, "error") %> prohibited this checkin from being saved:</h2>
<ul>
<% #pin.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<h3>Hi! Thank you for choosing to check-in with your teacher! This is a great way to get help, share your feelings and concerns, and make your school a safer place to learn. </h3>
<div class="form-group">
<%= label_tag(:classroom, "Select your classroom:") %>
<%= select_tag "pin[code]", options_from_collection_for_select(Classroom.all, "code", "code", ) %>
</div>
<h4>Where?</h4>
<% #causes.each do |cause| %>
<div class="checkbox">
<ul>
<li>
<%= check_box_tag "reflection[cause_ids][]", cause.id %>
<%= label_tag(cause.name) %>
</li>
<ul>
</div>
<% end %>
<div class="form-group">
<%= image_tag 'feelings.png', class: "image" %>
<h4>How are you feeling?</h4>
</div>
<% #emotions.each do |emotion| %>
<div class="checkbox">
<%= check_box_tag "pin[emotion_ids][]", emotion.id %>
<%= label_tag(emotion.name) %>
</div>
<% end %>
<div class="form-group">
<h4> You can <strong>free write </strong> </h4>
<p> I want my teacher to know _____________________________________.</p>
<%= f.text_area :question, class: "form-control" %>
</div>
<div class="form-group">
<h4> You can write about your own actions or thoughts here.</h4>
<p>Something I did was ________________________________.</p>
<%= f.text_area :question1, class: "form-control" %>
</div>
<div class="form-group">
<h4>You can write about the actions of another person here..</h4>
<p>Something __(name)_____did was___________________________________.</p>
<%= f.text_area :question2, class: "form-control" %>
</div>
<div class="form-group">
<h4>Do you have a question for your teacher?</h4>
<p>I want to ask my teacher ______________________________________.</p>
<%= f.text_area :question3, class: "form-control" %>
</div>
<div class="form-group">
<h4>Are you thinking about <strong>doing something else</strong>? You can write about it here.</h4>
<p>Something else I might do is ______________________________________.</p>
<%= f.text_area :question4, class: "form-control" %>
</div>
<div class="form-group">
<%= f.submit "submit", class: "btn btn-lg btn-primary" %>
</div>
<% end %>
EDIT [ ADDED pin_controller.rb]
class PinsController < ApplicationController
before_action :set_pin, only: [:show, :edit, :update, :destroy]
respond_to :html s
def home
#pins = Pin.all
respond_with(#pins)
authorize #pins
end
def show
respond_with(#pin)
end
def new
#pin = Pin.new
#emotions = Emotion.all
#causes = Cause.all
#school = School.find(params[:school])
respond_with(#pin)
authorize #pin
end
def edit
end
def create
code = params[:pin][:code]
#classroom = Classroom.where('code LIKE ?', code).first
unless #classroom
flash[:error] = "Classroom code incorrect"
#emotions = Emotion.all
#causes = Cause.all
render :new
else
params[:pin][:classroom_id] = #classroom.id
#pin = Pin.new(pin_params)
#pin.save
params[:pin][:cause_ids].each do |cause_id|
#cause = Cause.find(cause_id)
#pin.causes << #cause
end
params[:pin][:emotion_ids].each do |emotion_id|
#emotion = Emotion.find(emotion_id)
#pin.emotions << #emotion
end
if #pin.save
redirect_to signout_path and return
end
respond_with(#pin)
authorize #pin
end
end
def update
#pin.update(pin_params)
respond_with(#pin)
authorize #pin
end
def destroy
#pin.destroy
respond_with(#pin)
authorize #pin
end
private
def set_pin
#pin = Pin.find(params[:id])
authorize #pin
end
def pin_params
params.require(:pin).permit(:user_id, :question, :question1, :question2,
:question3, :question4, :question5, :classroom_id, :sad,
:happy, :mad, :brave, :embarrassed, :sorry, :frustrated,
:silly, :left_out, :excited, :hurt, :jealous, :confused,
:proud, :other)
end
end
Here's the exact error I'm getting
I've so far been unable to figure out the problem. What am I missing?

Answer 1

Stupid error but didn't catch it until I posted the form code... Thanks for the help!!
"reflection[cause_ids][]"
should be
"pin[cause_ids][]"
Thanks again for the help:)
<h4>Where?</h4>
<% #causes.each do |cause| %>
<div class="checkbox">
<ul>
<li>
<%= check_box_tag "reflection[cause_ids][]", cause.id %>
<%= label_tag(cause.name) %>
</li>
<ul>
</div>
<% end %>