How to use hidden_field_tag

Introduction

Since I used hidden_field_tag when creating the Rails application, it will be a memo of the contents at that time. Since the parameter did not skip when using the search function, it will be the content when corresponding using hidden_field_tag ^ ^

how to use

hidden_field and hidden_field_tag have similar uses but different uses. Whereas hidden_field is used in form_for and form_with,

You can use only one hidden_field_tag, and use it when you want to pass parameters by itself. It can also be used in form_for`.

Work content

There is a search window source like this.

:app/views/texts/index.html.erb

<%= search_form_for @eq do |f| %>
      <div class="d-flex">
        <div class="form-group flex-grow-1">
          <%= f.search_field :title_cont, placeholder: "Find teaching materials", class: "form-control" %>
        </div>
        <div> 
        <%= f.submit "Search", class: "btn btn-primary ml-1" %>
        </div>
      </div>
    <% end %>

The display of view is instructed by the controller like this.

app/controllers/texts_controller.rb

def index
    if params[:genre].nil? 
      @eq = Text.where(genre: ["Ruby on Rails", "Git","Basic","Ruby"]).ransack(params[:q])
    else
      @eq = Text.where(genre: params[:genre]).ransack(params[:q])
    end
      @texts = @eq.result.order(:id)
  end

Therefore Described in the index action if params [: genre] .nil? is a description that if the parameter is empty, ture will execute the following.

I have embedded genre: in the path of some pages.

<%= link_to " Ruby/Rails teaching materials", texts_path, class: "dropdown-item" %>
<%= link_to "Video teaching materials", movies_path, class: "dropdown-item" %>
<%= link_to "PHP teaching materials", texts_path(genre: "PHP"), class: "dropdown-item" %>
<%= link_to "Programming study session", movies_path(genre: "Live"), class: "dropdown-item" %>
<%= link_to "Question collection", questions_path, class: "dropdown-item" %>
.
.
.
.

The pages to be displayed are color-coded with [: genre]. So there is no problem if it is displayed from the link.

But,

This time, the purpose is search and display, so

At this rate Even if you search by keyword, there is no value in paramsofgenre, so it is displayed as true.

:app/views/texts/index.html.erb

<%= f.search_field :title_cont, placeholder: "Find teaching materials", class: "form-control" %>

↑ Even if you search for it as it is, only the character string entered by the user is skipped.

Terminal

Partial match search →"p"→ Search
 Parameters: {"q"=>{"title_cont"=>"p"}, "commit"=>"Search"}
  User Load (0.3ms)  SELECT "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 3], ["LIMIT", 1]]

From: /Users/ikedakeigo/Desktop/gyakuten_clone_group27/app/controllers/texts_controller.rb:4 TextsController#index:

     2: def index
     3:   binding.pry
 =>  4:   if params[:genre].nil? 
     5:     @eq = Text.where(genre: ["Ruby on Rails", "Git","Basic","Ruby"]).ransack(params[:q])
     6:   else
     7:     @eq = Text.where(genre: params[:genre]).ransack(params[:q])
     8:   end
     9:     @texts = @eq.result.order(:id)
    10: end

[1] pry(#<TextsController>)> params[:genre]
=> nil　⇦:There is no value in genre.

That's where hiddenfield_tag comes in! Let's send: genre alone.

:app/views/texts/index.html.erb

  <%= search_form_for @eq do |f| %>
      <div class="d-flex">
        <div class="form-group flex-grow-1">
          <%= f.search_field :title_cont, placeholder: "Find teaching materials", class: "form-control" %>
        </div>
        <div> 
        <%= hidden_field_tag(:genre, "Php")%>⇦ Add
        <%= f.submit "Search", class: "btn btn-primary ml-1" %>
        </div>
      </div>
    <% end %>

If you write it like this, you can skip the search keyword and: genre! But, If this is left as it is, the contents will always be Php and false will be returned, and only specific items can be searched.

Therefore, add a conditional branch to increase it flexibly.

:app/views/texts/index.html.erb

  <%= search_form_for @eq do |f| %>
      <div class="d-flex">
        <div class="form-group flex-grow-1">
          <%= f.search_field :title_cont, placeholder: "Find teaching materials", class: "form-control" %>
        </div>
        <div> 　　            
        <%= hidden_field_tag(:genre, params[:genre]) if params[:genre].present? %>⇦ Add
        <%= f.submit "Search", class: "btn btn-primary ml-1" %>
        </div>
      </div>
    <% end %>

The present? method is a conditional branch of " when "is present"

Since : genre is priced according to the page you are viewing, That's how I make the decision.

Now you can search the page by keyword! ^^

in conclusion

It may be quite normal to write code, but If you can do what you were worried about You may notice the end, "Hmm? No, you can understand it if you think about it normally!" ^^ lol

Don't give up on anything! ^^