ruby-on-rails - 用于有条件显示字段的 Rails 模式

Question

我发现自己一遍又一遍地重复这种类型的代码。

<% if <a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="2c0d6c4143484940025c5e435c495e5855024e404d4247" rel="noreferrer noopener nofollow">[email protected]</a>? %>
    <label>Property</label>
    <div><%= @model.property %></div>
<% end %>

目标是当且仅当值存在时才输出标签和属性值。我发现多次重复这段代码会导致很难扫描源代码。可以减少并使其更简洁吗？可以应用什么模式来简化编码？

Answer 1

您可以为您创建一个助手，它将自动处理这些测试:

# application helper
def display_if_exists(instance, attribute)
  return nil if instance.blank? || attribute.blank?

  label_tag = content_tag :label do
    instance.class.human_attribute_name attribute.to_sym
  end

  div_tag = content_tag :div do
    instance.try(attribute.to_sym)
  end

  return (label_tag + div_tag).html_safe
end

并以这种方式使用它:

# view
display_if_exists(@user, :username)

---

一点改进，有选项:

def display_if_exists(instance, attribute, options = {})
  return nil if instance.blank? || attribute.blank?

  label_options = options.delete(:label)
  div_options = options.delete(:div)

  label_tag = content_tag :label, label_options do
    instance.class.human_attribute_name attribute.to_sym
  end

  div_tag = content_tag :div, div_options do
    instance.try(attribute.to_sym)
  end

  return (label_tag + div_tag).html_safe
end

并使用如下选项:

display_if_exists(@user, :username, { label: { class: 'html-class' }, div: { style: 'margin-top: 2px;' } })

---

另一个选项是 Rails Presenter 模式。它非常有趣，但对于您想要实现的目标来说可能太深了:

• http://eewang.github.io/blog/2013/09/26/presenting-the-rails-presenter-pattern/
• http://fr.slideshare.net/mdesjardins/presenters-in-rails
• http://fr.slideshare.net/thaichor/presenter-and-decorator-in-rails
• Ruby on Rails patterns - decorator vs presenter