get request to new action using form instead of link causes param is missing or the value is empty error

[fugee ohu]

<%= form_tag new_item_path, :method => :get do %>

  <div class="field">
        <%= select_tag(:item_type, options_for_select(Item::ITEM_TYPES)) %>
  </div>

<div class="actions">
    <%= submit_tag "New item" %>
</div>

ActionController::ParameterMissing in ItemsController#new

param is missing or the value is empty: item

In my controller I have the usual filter

    def item_params
      params.require(:item).permit(:item_type, :title,  :item_id, item_ids: [])
    end

...

Started GET "/items/new?item_type=General&commit=New+item&utf8=%E2%9C%93" for 127.0.0.1 at 2019-10-04 03:32:18 -0400

Processing by ItemsController#new as HTML
  Parameters: {"item_type"=>"General", "commit"=>"New item", "utf8"=>"✓"}
Completed 400 Bad Request in 2ms (ActiveRecord: 0.0ms)


 
ActionController::ParameterMissing (param is missing or the value is empty: item):
 
app/controllers/items_controller.rb:109:in `item_params'
app/controllers/items_controller.rb:23:in `new'
 ...

[Avdhesh Sharma (ROR)]

Because in form_tag we don't define scope so all parameters comes in params directry.

so you need to fix item_params method

params.permit(:item_type) to permit parameters

your's item_params method is written to permit this params structure
{item: {item_type: q}

[fugee ohu]

What does this do?

      if params.fetch(:item, {}).fetch(:item_type, false)

[Ariel Juodziukynas]

https://apidock.com/ruby/Hash/fetch

fetch tries to get the value from a hash given a key, the second parameter is a fallback in case the key does not exist on the hash (params), in your case, if params[:item] does not exist, it returns {} so the next .fetch won't fail. now the second .fetch tries to get the value for the key :item_type, if it does not exist y returns "false". fetch is used when you have optional keys on a hash and you need a fallback in case the key is not present

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