在Rails中，如何在使用javascript_include_tag之前检查javascript文件是否存在 [英] In Rails how to check if javascript file exists before using javascript_include_tag

问题描述

在Rails 3.2应用程序中，我想在资产管道中包含javascript_include_tag之前检查资产管道中是否存在javascript文件.像这样:

In a rails 3.2 app, I would like to check for the existence of a javascript file in the asset pipeline before including the javascript_include_tag in a file. Something like:

<% if javascript_file_exists? %>
  <%= javascript_include_tag "#{controller_name}_controller" %>
<% end %>

我想这样做，以便没有javascript文件不会导致错误.有办法吗?

I would like to do this so that the absence of a javascript file will not result in an error. Is there a way to do this?

推荐答案

Rails的另一种方法是使用帮助器.这使您可以检查文件的coffeescript或javascript版本:

A more Rails way is to use a helper. This allows you to check for a coffeescript or a javascript version of a file:

def javascript_exists?(script)
  script = "#{Rails.root}/app/assets/javascripts/#{params[:controller]}.js"
  File.exists?(script) || File.exists?("#{script}.coffee") 
end

然后您可以在布局中使用它:

Then you can use it in your layout:

<%= javascript_include_tag params[:controller], :media => "all"  if javascript_exists?(params[:controller]) %>

您可以对CSS执行相同操作:

You can do the same with your CSS:

 -- helper --
 def stylesheet_exists?(stylesheet)
   stylesheet = "#{Rails.root}/app/assets/stylesheets/#{params[:controller]}.css"
   File.exists?(stylesheet) || File.exists?("#{stylesheet}.scss") 
 end

 -- layout --
 <%= stylesheet_link_tag params[:controller], :media => "all"  if stylesheet_exists?(params[:controller]) %>

已更新#javascript_exists?

我最近对我的javascript_exists?助手做了一些更改:

I have recently made some changes to my javascript_exists? helper:

def javascript_exists?(script)
  script = "#{Rails.root}/app/assets/javascripts/#{script}.js"
  extensions = %w(.coffee .erb .coffee.erb) + [""]
  extensions.inject(false) do |truth, extension|
    truth || File.exists?("#{script}#{extension}")
  end
end

在应用程序布局中调用它:

call it in the application layout:

<%= javascript_include_tag params[:controller]  if javascript_exists?(params[:controller]) %>

现在它将处理更多扩展名，并使用注入确定文件是否存在.然后，您可以根据应用程序的需要向扩展数组添加更多扩展.

This will now handle more extensions and use an inject to determine if the file exists. You can then add a bunch more extensions to the extensions array, as needed for your app.

编辑DEUX:更新了#stylesheet_exists?

相同，但适用于样式表:

Same, but for stylesheets:

def stylesheet_exists?(stylesheet)
  stylesheet = "#{Rails.root}/app/assets/stylesheets/#{stylesheet}.css"
  extensions = %w(.scss .erb .scss.erb) + [""]
  extensions.inject(false) do |truth, extension|
    truth || File.exists?("#{stylesheet}#{extension}")
  end
end

编辑最后(可能):将其干燥

def asset_exists?(subdirectory, filename)
  File.exists?(File.join(Rails.root, 'app', 'assets', subdirectory, filename))
end

def image_exists?(image)
  asset_exists?('images', image)
end

def javascript_exists?(script)
  extensions = %w(.coffee .erb .coffee.erb) + [""]
  extensions.inject(false) do |truth, extension|
    truth || asset_exists?('javascripts', "#{script}.js#{extension}")
  end
end

def stylesheet_exists?(stylesheet)
  extensions = %w(.scss .erb .scss.erb) + [""]
  extensions.inject(false) do |truth, extension|
    truth || asset_exists?('stylesheets', "#{stylesheet}.css#{extension}")
  end
end

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