Ruby-on-rails 如何在 rails 表单中有一个下拉 <select> 字段？

How to have a drop down <select> field in a rails form?

提问by iCyborg

I am creating a scaffold -

我正在创建一个脚手架 -

rails g scaffold Contact email:string email_provider:string 

but I want the email provider to be a drop down (with gmail/yahoo/msn as options) and not a text field. How can I do this ?

但我希望电子邮件提供商是一个下拉列表（使用 gmail/yahoo/msn 作为选项）而不是文本字段。我怎样才能做到这一点 ？

回答by R Milushev

You can take a look at the Rails documentation. Anyways , in your form :

您可以查看Rails 文档。无论如何，以您的形式：

  <%= f.collection_select :provider_id, Provider.order(:name),:id,:name, include_blank: true %>

As you can guess , you should predefine email-providers in another model -Provider, to have where to select them from .

您可以猜到，您应该在另一个模型中预定义电子邮件提供商 - Provider，以便从中选择它们。

回答by Fdwillis

Or for custom options

或自定义选项

<%= f.select :desired_attribute, ['option1', 'option2']%>

回答by Michael Durrant

You create the collection in the Contactcontroller -

您在Contact控制器中创建集合-

app/controllers/contacts_controller.erb 

Adding

添加

@providers = Provider.all.by_name

to the new, create and edit methods, using a scope for the by_namein the Providermodel - app/models/provider.rb- for the ordering by name

新，创建和编辑方法，使用范围为by_name在Provider模型- app/models/provider.rb-按名称排序

scope by_name  order(:name)

Then in the view - app/views/contacts/_form.html.erb- you use

然后在视图中app/views/contacts/_form.html.erb——你使用

<%= f.collection_select :provider_id, @providers, :id, :name, include_blank: true %>

For rails forms, I also strongly recommend you look at a form builder like simple_form - https://github.com/plataformatec/simple_form- which will do all the heavy lifting.

对于 rails 表单，我还强烈建议您查看像 simple_form 这样的表单构建器 - https://github.com/plataformatec/simple_form- 它将完成所有繁重的工作。

回答by phobos

This is a long way round, but if you have not yet implemented then you can originally create your models this way. The method below describes altering an existing database.

这是一个很长的路要走，但是如果您还没有实现，那么您最初可以通过这种方式创建模型。下面的方法描述了更改现有数据库。

1) Create a new model for the email providers:
$ rails g model provider name

1）为电子邮件提供商创建一个新模型：
$ rails g model provider name

2) This will create your model with a name string and timestamps. It also creates the migration which we need to add to the schema with:
$ rake db:migrate

2) 这将使用名称字符串和时间戳创建您的模型。它还创建了我们需要添加到架构中的迁移：
$ rake db:migrate

3) Add a migration to add the providers ID into the Contact:
$ rails g migration AddProviderRefToContacts provider:references

3) 添加迁移以将提供者 ID 添加到联系人中：
$ rails g migration AddProviderRefToContacts provider:references

4) Go over the migration file to check it look OK, and migrate that too:
$ rake db:migrate

4）检查迁移文件以检查它是否正常，然后也迁移它：
$ rake db:migrate

5) Okay, now we have a provider_id, we no longer need the original email_provider string:
$ rails g migration RemoveEmailProviderFromContacts

5) 好的，现在我们有了 provider_id，我们不再需要原来的 email_provider 字符串：
$ rails g migration RemoveEmailProviderFromContacts

6) Inside the migration file, add the change which will look something like:

6) 在迁移文件中，添加如下所示的更改：

class RemoveEmailProviderFromContacts < ActiveRecord::Migration
  def change
    remove_column :contacts, :email_provider
  end
end

7) Once that is done, migrate the change:
$ rake db:migrate

7) 完成后，迁移更改：
$ rake db:migrate

8) Let's take this moment to update our models:
Contact: belongs_to :provider
Provider: has_many :contacts

8) 让我们花点时间更新我们的模型：
联系方式：belongs_to :provider
提供者：has_many :contacts

9) Then, we set up the drop down logic in the _form.html.erb partial in the views:

9) 然后，我们在视图的_form.html.erb 部分中设置下拉逻辑：

  <div class="field">
    <%= f.label :provider %><br>
    <%= f.collection_select :provider_id, Provider.all, :id, :name %>
  </div>

10) Finally, we need to add the provders themselves. One way top do that would be to use the seed file:

10）最后，我们需要自己添加提供者。这样做的一种方法是使用种子文件：

Provider.destroy_all

gmail = Provider.create!(name: "gmail")
yahoo = Provider.create!(name: "yahoo")
msn = Provider.create!(name: "msn")

$ rake db:seed

$ rake db:seed

回答by Raghvendra Parashar

Please have a look here

请看这里

Either you can use rails tag Or use plain HTML tags

您可以使用 rails 标记或使用纯 HTML 标记

Rails tag

Rails 标签

<%= select("Contact", "email_provider", Contact::PROVIDERS, {:include_blank => true}) %>

*above line of code would become HTML code(HTML Tag), find it below *

*上面的代码行会变成 HTML 代码（HTML 标签），在下面找到它 *

HTML tag

HTML 标签

<select name="Contact[email_provider]">
  <option></option>
  <option>yahoo</option>
  <option>gmail</option>
  <option>msn</option>
</select>

回答by gsumk

<%= f.select :email_provider, ["gmail","yahoo","msn"]%>

<%= f.select :email_provider, ["gmail","yahoo","msn"]%>

回答by konyak

In your model,

在你的模型中，

class Contact
  self.email_providers = %w[Gmail Yahoo MSN]
  validates :email_provider, :inclusion => email_providers
end

In your form,

在你的表格中，

<%= f.select :email_provider, 
    options_for_select(Contact.email_providers, @contact.email_provider) %>

the second arg of the options_for_select will have any current email_provider selected.

options_for_select 的第二个参数将选择任何当前的 email_provider。

回答by sivamani

Rails drop down using has_many association for article and category:

Rails 下拉使用 has_many 关联文章和类别：

has_many :articles

belongs_to :category

<%= form.select :category_id,Category.all.pluck(:name,:id),{prompt:'select'},{class: "form-control"}%>