Ruby on Rails：下拉菜单

Question

I'm trying to create a drop down menu to allow a user to change an entry's field in my table. The user has one of three options -- hot, medium and cold.

I already have text_fields that do essentially the same thing for other fields, that all update when the user clicks on a submit_tag .

Is there an easy way to implement a drop-down box and have the result saved with the submit_tag ?

thanks,

-Chris

Answer 1

Here's the basic answer. The array of two element arrays is the critical part.

<% form_for @entry do |f| %>
  <%= f.text_field :name %>
  <%= f.select :temperature, [['Hot','hot'],['Medium','medium'],['Cold','cold']] %>
  <%= f.submit %>
<% end %>

Answer 2

I'll assume 2 things:

• That you are the <%= form_for @model_instance idiom (explained on section 2.2 of this guide ).
• That you want to store the "hot", "medium" and "cold" values as strings (not as numbers 1,2 and 3 or something similar) on your database.

Let's say that you have two fields, called :name and :temperature , controlled by two text_fields :

<% form_for @article do |f| %>
  <%= f.text_field :name %>
  <%= f.text_field :temperature %>
  <%= f.submit "Create" %> <% end %>
<% end %>

Now you want to change the :temperature control to a dropdown list, accepting hot, medium and cold as values. Then you can do that this way:

<% form_for @article do |f| %>
  <%= f.text_field :name %>
  <%= f.collection_select :temperature, Article::TEMPERATURES, :to_s, :to_s, 
       :include_blank => true
  %>
  <%= f.submit "Create" %> <% end %>
<% end %>

You will now have to define the Article::TEMPERATURES constant in your Article model. It shouldn't be very difficult:

class Article < Activerecord::Base

  TEMPERATURES = ['hot', 'medium', 'cold']

You may be wondering why I added the :include_blank part on the collection_select . This will add an "empty" option on your dropdown list. You will need that empty option when creating new objects, unless you want a "default" value to temperature.

Answer 3

http://api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html#M001730

Answer 4

I was working on something similar. I got this to work by simply adding either an enum or a constant(similar to what kikito said previously) in my model and then calling the select in my form.

Here's how it can work.

using the constant:

class ClassName < ActiveRecord::Base TEMPERATURES = ['Hot', 'Medium', 'Cold'] end

bin/rails g migration add_column_to_table temperatures:string

_form.html.erb

<%= f.label :temperature %>
<%= f.select :temperature, ClassName::TEMPERATURE %>

or

using the enum:

class ClassName < ActiveRecord::Base enum temperature: [:hot, :medium, :cold] end

bin/rails g migration add_column_to_table temperatures:integer

_form.html.erb

<%= f.label :temperature %>
<%= f.select :temperature, ClassName.temperatures.keys %>

Hope that helps you!

Answer 5

You might want to consider formtastic gem which is lot less code.

<% semantic_form_for @stuff do |f| %>  
   <% f.inputs do %>  
   <%= f.input :name %>  
   <%= f.input :temperature, :as => :select, 
               :label => "Degree", :include_blank => false,
               :collection => [["Hot", 1], ["Medium", 2], ["Cold", 3]] %>  
   <% end %>  
   <%= f.buttons %>    
<% end %>  

Answer 6

In accordance with all of the above answers, remember to do this last, important step:

Restart your server !

As a newbie, I was wondering why my array was not working even though I followed all the steps correctly.