Ruby on Rails form_for creates empty object - ruby-on-rails

Question

I have a partial named _form.html.erb in my alerts/views/ folder. I render that partial from the show page in my agencies/views/ folder.
Everything renders properly, and the partial does create a new alert, but the alert is completely empty.
alerts_controller create method
def create
#alert = Alert.new(body: params[:body],
severity: params[:severity],
agency_id: #current_member.id)
respond_to do |format|
if #alert.save
format.html { redirect_to #alert.agency, notice: 'Alert was successfully created.' }
format.json { render :show, status: :created, location: #alert}
else
format.html { render :new }
format.json { render json: #alert.errors, status: :unprocessable_entity }
end
end
end
_form.html.erb
<%= form_for(Alert.new) do |f| %>
<div class="input-group">
<div class="field">
<%= f.label :body %><br>
<%= f.text_field :body %>
</div>
<div class="field">
<%= f.label :severity %><br>
<%= f.number_field :severity %>
</div>
<div class="action">
<%= f.submit %>
</div>
</div>
<% end %>
There are no errors, except that the alert created is completely empty. The body, severity, and agency_id variables are all nil.
I have tried replacing the line
<%= form_for(Alert.new) do |f| %>
with this:
<%= form_for(#alert) do |f| %>
and adding this line:
#alert = Alert.new
to the show method in the agency controller.
But the same thing happens either way. What am I doing wrong?
EDIT
This is the log starting when I hit submit, and ending before loading the redirect in the alerts.create method.
Started POST "/alerts" for ::1 at 2016-03-31 18:29:43 -0400
Processing by AlertsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"CgpepnYUec9uUoE/Ys6SAkOlzmK+w2q9IN782sXNoXnB3UyuegiS6m+W+mW+nXu4EIL8P8xH6JdigU8FfmzhVw==", "alert"=>{"body"=>"This is the body text", "severity"=>"12345"}, "commit"=>"Create Alert"}
Account Load (0.1ms) SELECT "accounts".* FROM "accounts" WHERE "accounts"."id" = ? LIMIT 1 [["id", 7]]
Agency Load (0.1ms) SELECT "agencies".* FROM "agencies" WHERE "agencies"."id" = ? LIMIT 1 [["id", 2]]
(0.1ms) begin transaction
SQL (0.2ms) INSERT INTO "alerts" ("agency_id", "created_at", "updated_at") VALUES (?, ?, ?) [["agency_id", 2], ["created_at", "2016-03-31 22:29:43.014846"], ["updated_at", "2016-03-31 22:29:43.014846"]]
(135.8ms) commit transaction
Agency Load (0.1ms) SELECT "agencies".* FROM "agencies" WHERE "agencies"."id" = ? LIMIT 1 [["id", 2]]
Redirected to http://localhost:3000/agencies/2
Completed 302 Found in 141ms (ActiveRecord: 136.2ms)
When I comment out the alerts.create method and add this line:
render plain: params
This is the output:
{"utf8"=>"✓",
"authenticity_token"=>"3OfteFX41SV/5NxpTcKbP7AKhLm/ZKah+NXVn84e2xwXMP9wWeQ+AH4gpzORkXKF4y225M3gJIu6imZAdb+bMg==",
"alert"=>{"body"=>"This is the body text.", "severity"=>"12345"},
"commit"=>"Create Alert", "controller"=>"alerts", "action"=>"create"}

Answer 1

The root cause is evident from your params debugging. The params hash has an alert key in it. The alert value is a hash of body and severity.
In your controller, you reference params[:body] and params[:severity]. Those should be params[:alert][:body] and params[:alert][:severity].
Was there a reason not to use Rails' strong parameters? You could refactor to something like:
def create
#alert = Alert.new(alert_params.merge(agency_id: #current_member.id)
…
end
…
private
def alert_params
params.require(:alert).permit(:body, :severity)
end

Answer 2

In the create method params supposed to be like this.
Because your params "alert"=>{"body"=>"This is the body text.", "severity"=>"12345"}
def create
#alert = Alert.new(body: params[:alert][:body],
severity: params[:alert][:severity],
agency_id: #current_member.id)
respond_to do |format|
if #alert.save
format.html { redirect_to #alert.agency, notice: 'Alert was successfully created.' }
format.json { render :show, status: :created, location: #alert}
else
format.html { render :new }
format.json { render json: #alert.errors, status: :unprocessable_entity }
end
end
end