ruby-on-rails - 如果数据为空、nil 或空白，则返回字符串？

Question

如果特定对象为空、nil 或空白，我有一个text_area我想设置的属性。placeholder

我目前正在这样做：

<%= f.text_area :comment, placeholder: @response.followup ||= "Would you like to add a note?" %>

如果@response.followupis ，这似乎有效nil，但如果它只是空的......它不使用"Would you like to add a note?"我设置的默认文本。

score 4 · Accepted Answer

检查您的 Rails 版本是否presence可用。如果是，您可以执行以下操作

<%= f.text_area :comment, placeholder: @response.followup.presence || "Would you like to add a note?" %>

如果它不可用，您可以选择以下之一

使用装饰者/演示者（我认为这是矫枉过正）
在控制器中设置占位符的值

@response.followup = 'Would you like to add a note?' if response.blank?
在视图中使用三元运算符

<%= f.text_area :comment, placeholder: (@response.followup.blank? ? "Would you like to add a note?" : @response.followup) %>

score 0 · Accepted Answer

您应该能够测试“空白”并使用：

placeholder: !@response.followup.blank? ? @response.followup : "Would you like to add a note?"

因此，如果后续内容不为空，则使用它，否则使用您的默认文本。

score 0 · Accepted Answer

<%= f.text_area :comment, placeholder: (@response.followup.blank? ? "Would you like to add a note?" : @response.followup) %>

也许

<%= f.text_area :comment, placeholder: (@response.followup.present? ? @response.followup : "Would you like to add a note?") %>

如果你发现读起来更好。

score 0 · Accepted Answer

我经常这样做，我不得不做这样的事情：

class Object
  def fill(wtf)
    present? ? self : wtf
  end
end

<%= f.text_area :comment, placeholder: @response.followup.fill("Would you like to add a note?") %>

例子：

require 'active_support/core_ext/object/blank'

class Object
  def fill(wtf)
    present? ? self : wtf
  end
end

p nil.fill("omg")

score 0 · Accepted Answer

使用礼物？方法

<%= f.text_area :comment, placeholder: (@response.followup.present? ? "Would you like to add a note?" : @response.followup) %>

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