在常见的 Rails 表单场景中，我们时常需要用到 select 下拉选择框，然而这部分我发现一直都挺麻烦的，而且不规范，没一个统一方案。

<%= form_with(model: post, local: true) do |form| %>
  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

  <div class="field">
    <%= form.label :category_id %>
    <%= form.select :category_id, Category.where("parent_id is null and depth = 0").order("name asc").all.map { |category| [category.name, category.id] } %>
  </div>

  <div class="actions">
    <%= form.submit %>
  </div>
<% end %>

于是在很多的 Rails 项目里面常常会看到这样一行代码：

<%= form.select :category_id, Category.where("parent_id is null and depth = 0").order("name asc").all.map { |category| [category.name, category.id] } %>

为了解决这个繁琐的问题，我实现一个 form-select

class Category
  form_select :name, scope: -> { where("parent_id is null and depth = 0").order("name asc") }
  form_select :reverse_name, field: [:name, :id], scope: -> { order("name desc") }
end

class User
  form_select :login, field: [:login, :to_param], scope: -> { order("id desc") }
  form_select :email
  form_select :email_value, field: :email
  form_select :city, field: :city, scope: -> { where("city is not null").select(:city).distinct }

  def to_param
    login.downcase
  end
end

class Post
  form_select :author, field: [:author], scope: -> { where("author is not null").select(:author).distinct }
end

通过在 Model 中使用 form_select 来定义下拉选项的别名函数，我们就可以得到这样的结果：

irb> Category.name_options
 => [["Android", 3], ["iOS", 2], ["News", 1]]

irb> Category.reverse_name_options
 => [["News", 1], ["iOS", 2], ["Android", 3]]

irb> User.login_options
 => [["Foo", "foo"], ["Mike", "mike"], ["Jason", "jason"]]

irb> User.email_options
 => [["[email protected]", 10], ["[email protected]", 11], ["[email protected]", 12]]

irb> User.email_value_options
 => [["[email protected]", "[email protected]"], ["[email protected]", "[email protected]"], ["[email protected]", "[email protected]"]]

irb> User.city_options
 => [["NewYork", "NewYork"], ["San Francisco", "San Francisco"], ["Chicago", "Chicago"]]

irb> Post.author_options
 => [["Jason", "Jason"], ["Mike", "Mike"], ["Foor", "Foo"]]

于是在 View 里面就可以直接使用了：

<div class="field">
  <%= form.label :category_id %>
  <%= form.select :category_id, Category.name_options %>
</div>

<div class="field">
  <%= form.label :user_id %>
  <%= form.select :user_id, User.email_options %>
</div>

<div class="field">
  <%= form.label :city %>
  <%= form.select :city, User.city_options %>
</div>

这样做带来的好处：

• 一些需要反复在好多 Views 用的 Select Options 无需在 Views 里面写重复逻辑了
• 便于写测试验证，比如：model_test.rb

项目地址

https://github.com/rails-engine/form-select